1. It is a well-established rule of customary international law that neutral civilian aircraft are liable to interception,^[697] in order to enable Belligerent Parties to verify their true character or whether they are employed in their innocent role. In most cases, interception of neutral civilian aircraft will be sufficient to establish whether they in fact have neutral character and are not employed in any of the activities referred to in Rules 140-141. Following interception, the neutral civilian aircraft may be ordered to land for inspection. Inspection can also be carried out when the neutral civilian aircraft is encountered on the ground.
2. Neutral State aircraft, including neutral military aircraft, enjoy sovereign immunity and may not be interfered with, unless they are engaged in activities in support of the enemy’s military actions (see paragraph 6 of the Commentary on Rule 1 (cc)).
3. Interception of neutral civilian aircraft must always be conducted with due regard to their safety. ICAO has published a Manual on the interception of civil aircraft^[698] that may be considered as reflecting customary international peacetime law. While the recommendations given and the procedures described in the ICAO Manual do not necessarily apply in times of armed conflict,^[699] they ought to serve as a useful guidance for interception of civilian aircraft even by Belligerent Parties.
4. In any event, under the law of international armed conflict: “Belligerent States should promulgate and adhere to safe procedures for intercepting civil aircraft as issued by the competent international organization.” See Para. 128 of the SRM/ACS^[700] and Para. 12.84 of the UK Manual.^[701] Furthermore, as an additional example, see the detailed interception procedures issued by the US Federal Aviation Administration.^[702]
5. As per Rule 17 (b), only military aircraft are entitled to intercept neutral civilian aircraft.

697. Art. 49 of the HRAW: “Private aircraft are liable to visit and search and to capture by belligerent military aircraft.”
698. International Civil Aviation Organization, Manual concerning Interception of Civil Aircraft (2^nd ed. 1990), ICAO Doc. 9433-AN/926.
699. This especially holds true for Principle 2.5 lit. a) of the ICAO Manual concerning Interception of Civil Aircraft, which states at 2-1: “interception of civil aircraft will be undertaken only as a last resort.”
700. Para. 128 of the SRM/ACS: “Belligerent States should promulgate and adhere to safe procedures for intercepting civil aircraft as issued by the competent international organisation.”
701. Para. 12.84 of the UK Manual: “Belligerent states should promulgate and adhere to safe procedures for intercepting civil aircraft as issued by the competent international organization.”
702. US Federal Aviation Administration, Aeronautical Administration Manual, Official Guide to Basic Flight Information and ATC procedures, Chapter 5 (“Air Traffic Procedures”), Section 6 (“National Security and Interception Procedures”, available via http://www.faa.gov/air_traffic/publications/ATpubs/AIM/chap5toc.htm. Interception procedures are dealt with in Section 5.6.2.:
     “5.1 In phase 1 — approach phase — the aircraft to be intercepted will be approached from the stern by two intercepting military aircraft. At night or in Instrument Meteorological Conditions (e.g. fog), a radar trail tactic will be used.
     5.2 In phase 2 — identification phase — the intercepted aircraft ought to expect to visually acquire the lead interceptor and possibly the wingman. The wingman will assume a surveillance position while the flight leader approaches the intercepted aircraft.
     5.3 In phase 3 — post intercept phase — after identification of the aircraft by type, nationality, etc., the flight leader will turn away from the intercepted aircraft. The wingman will remain well clear and accomplish a rejoin with the leader.”

1. If the information acquired during interception is unsatisfactory, and if the grounds for suspicion continue to exist or have been reinforced, the neutral civilian aircraft may be ordered to proceed to a sufficiently safe airfield under the control of the intercepting Belligerent Party or its co-belligerents.
2. On the ground, the aircraft may be inspected. Inspection is limited to such measures that are necessary to verify whether the neutral civilian aircraft is engaged in activities rendering it liable to capture. Hence, a physical inspection of the aircraft will be the exception rather than the rule. In most cases, an inspection of the aircraft’s documents will be sufficient to verify that it is not engaged in activities rendering it liable to capture under Rule 140.
3. Notwithstanding the position taken by Art. 58^[703] and Art. 59^[704] of the HRAW, the Group of Experts has reached the conclusion that — unlike captured enemy civilian aircraft (see Rule 135) — captured neutral civilian aircraft may not be destroyed, even as an exceptional measure.

703. Art. 58 of the HRAW, see fn. 691.
704. Art. 59 of the HRAW, see fn. 692.

1. In some situations, the intercepting Belligerent Party may prefer to divert the aircraft from its declared destination, instead of exercising the right of inspection. Similarly, the crew of the neutral civilian aircraft may prefer to proceed to a new destination rather than go to a belligerent airfield and be subjected to inspection. Accordingly, Rule 137 (c) provides for an alternative to capture by diverting the aircraft from its destination.^[705]
2. However, since neutral civilian aircraft are not under an obligation to comply with a diversion order, the consent of the neutral civilian aircraft is required. It may be recalled in this context that consent is not required to divert an enemy civilian aircraft from its declared destination (see Rule 134).

705. Para. 126 of the SRM/ACS: “As an alternative to visit and search: (a) an enemy civil aircraft may be diverted from its declared destination; (b) a neutral civil aircraft may be diverted from its declared destination with its consent.”

1. This Rule is based on Para. 132 of the SRM/ACS.^[706]
2. Interception, inspection or diversion of neutral civilian aircraft may entail considerable financial losses for the operators of the affected aircraft, as well as for the owners of the cargo on board. Such measures will also tie up belligerent forces that could be used elsewhere. Additionally, they can place such forces at risk. These problems were partially solved by Great Britain and its allies in WWI and WWII through introduction of the “navicert” system.^[707]
3. Today, the right to issue such certificates is widely recognized and is considered to also apply to neutral civilian aircraft. Accordingly, a Belligerent Party is entitled to issue “aircerts” certifying, after inspection in neutral territory, that the aircraft is not carrying contraband.
4. Notwithstanding the previous issuance of an “aircert”, a Belligerent Party remains entitled to insist on further inspection of the neutral civilian aircraft in light of new developments or new information.

706. Para. 132 of the SRM/ACS: “In order to avoid the necessity of visit and search, belligerent States may establish reasonable measures for the inspection of cargo of neutral civil aircraft and certification that an aircraft is not carrying contraband.”
     Para. 12.88 of the UK Manual contains an identical provision.
707. Para. 7.4.2 of NWP (“Certificate of Noncontraband carriage”): “A certificate of noncontraband carriage is a document issued by a belligerent consular or other designated official to a neutral vessel (navicert) or neutral aircraft (aircert) certifying that the cargo being carried has been examined, usually at the initial place of departure, and has been found to be free of contraband. The purpose of such a navicert or aircert is to facilitate belligerent control of contraband goods with minimal interference and delay of neutral commerce. The certificate is not a guarantee that the vessel or aircraft will not be subject to visit and search or that cargo will not be seized. (Changed circumstances, such as a change in status of the neutral vessel, between the time of issuance of the certificate and the time of interception at sea may cause it to be invalidated.) Conversely, absence of a navicert or aircert is not, in itself, a valid ground for seizure of cargo. Navicerts and aircerts issued by one belligerent have no effect on the visit and search rights of a belligerent of the opposing side. The acceptance of a navicert or aircert by a neutral ship or aircraft does not constitute ‘unneutral service.’”
     Para. 13.97 of the UK Manual: “In order to obviate the necessity for visit and search, neutral states are encouraged to enforce reasonable control measures and certification procedures to ensure that their merchant vessels are not carrying contraband.”

1. This Rule is based on Para. 133 of the SRM/ACS.^[708]
2. Because of the doubts raised — especially during WWII — as to the consequences of carrying a navicert issued by a Belligerent Party, the Group of Experts considered it necessary to stress that the mere carrying of an “aircert” does not render the neutral civilian aircraft liable to capture by the enemy.
3. The expression “unneutral service” is long-standing in the law of international armed conflict, and is defined in detail in Chapter III of the 1909 London Declaration.^[709] The thrust of the definition is that the neutral vessel (in this case: aircraft) engages in activities that are inconsistent with its neutral character.

708. Para. 133 of the SRM/ACS: “The fact that a neutral civil aircraft has submitted to such measures of supervision as the inspection of its cargo and grant of certificates of non-contraband cargo by one belligerent is not an act of unneutral service with regard to an opposing belligerent.”
     Para. 12.89 of the UK Manual contains an identical provision.
709. Chapter III of the London Declaration is entitled “Unneutral Service”. See, in particular, Art. 45 of the 1909 London Declaration: “A neutral vessel will be condemned and will, in a general way, receive the same treatment as a neutral vessel liable to condemnation for carriage of contraband: (1) If she is on a voyage especially undertaken with a view to the transport of individual passengers who are embodied in the armed forces of the enemy, or with a view to the transmission of intelligence in the interest of the enemy. (2) If, to the knowledge of either the owner, the charterer, or the master, she is transporting a military detachment of the enemy, or one or more persons who, in the course of the voyage, directly assist the operations of the enemy. In the cases specified under the above heads, goods belonging to the owner of the vessel are likewise liable to condemnation. The provisions of the present Article do not apply if the vessel is encountered at sea while unaware of the outbreak of hostilities, or if the master, after becoming aware of the outbreak of hostilities, has had no opportunity of disembarking the passengers. The vessel is deemed to be aware of the existence of a state of war if she left an enemy port subsequently to the outbreak of hostilities, or a neutral port subsequently to the notification of the outbreak of hostilities to the Power to which such port belongs, provided that such notification was made in sufficient time.”

1. Capture as prize is a belligerent act and may therefore not be exercised within neutral territory. It is made clear in Rule 140 that the determination that a neutral civilian aircraft is liable to capture need not be based on the results of an inspection. The captor Belligerent Party may rely on intelligence or other information to determine that a neutral civilian aircraft is liable to capture as prize. As long as the information thus gained is sufficient to establish one of the conditions laid down in Rule 140 (a) − (f), there is no need for a prior exercise of inspection. If, however, the source of the information cannot be disclosed, the aircraft ought to be inspected in order to enable the prize court to adjudicate on the legality of capture.
2. The conditions rendering a neutral civilian aircraft liable to capture are generally recognized as reflecting customary international law (see Art. 53 of the HRAW^[710] and Para. 153 of the SRM/ACS).^[711]

710. Art. 53 of the HRAW: “A neutral private aircraft is liable to capture if it: (a) Resists the legitimate exercise of belligerent rights; (b) Violates a prohibition of which it has had notice issued by a belligerent commanding officer under Article 30; (c) Is engaged in unneutral service; (d) Is armed in time of war when outside the jurisdiction of its own country; (e) Has no external marks or uses false marks; (f) Has no papers or insufficient or irregular papers; (g) Is manifestly out of the line between the point of departure and the point of destination indicated in its papers and after such enquiries as the belligerent may deem necessary, no good cause is shown for the deviation. The aircraft, together with its crew and passengers, if any, may be detained by the belligerent, pending such inquiries; (h) Carries, or itself constitutes, contraband of war; (i) Is engaged in breach of a blockade duly established and effectively maintained; (k) [sic] Has been transferred from belligerent to neutral nationality at a date and in circumstances indicating an intention of evading the consequences in which an enemy aircraft, as such, is exposed. Provided that in each case (except (k)) the ground for capture shall be an act carried out in the flight in which the neutral aircraft came into belligerent hands, i.e., since it left its point of departure and before it reached its point of destination.”
711. Para. 153 of the SRM/ACS: “Neutral civil aircraft are subject to capture outside neutral airspace if they are engaged in any of the activities in paragraph 70 or if it is determined as a result of visit and search or by any other means, that they: (a) are carrying contraband; (b) are on a flight especially undertaken with a view to the transport of individual passengers who are embodied in the armed forces of the enemy; (c) are operating directly under enemy control, orders, charter, employment or direction; (d) present irregular or fraudulent documents, lack necessary documents, or destroy, deface or conceal documents; (e) are violating regulations established by a belligerent within the immediate area of naval operations; or (f) are engaged in a breach of blockade.”

1. This Rule is based on Art. 53 (h) of the HRAW^[712] and on Para. 153 (a) of the SRM/ACS.^[713]
2. Neutral civilian aircraft continue to enjoy the rights of pursuing their commercial activities, even when an international armed conflict is going in. These rights include the transportation of goods, regardless of whether they are neutral or enemy in character. However, neutral civilian aircraft are not free to transport contraband.
3. According to Rule 1 (n), “contraband means goods which are ultimately destined for territory under the control of an enemy Belligerent Party and which are susceptible for use in international armed conflict”. Hence, ownership — be it enemy or neutral — is irrelevant.
4. Rule 140 (a) reflects State practice that has lead to an abolition of the traditional distinction between “absolute” and “relative” contraband (see Commentary on Rule 1 (n)). Moreover, it is not necessary that the goods considered contraband are contained in a contraband list. It is sufficient to establish that the goods are susceptible to belligerent use and that they are ultimately destined for territory under the control of an en-emy Belligerent Party. However, for reasons of legal clarity, Belligerent Parties ought to publish contraband lists prior to the exercise of prize measures.^[714]
5. The fact that the goods in question must be “ultimately destined for territory under the control” of the enemy confirms the validity of the “doctrine of continuous voyage”. According to the aircraft’s papers, the goods may appear to be destined for neutral territory. Nevertheless, the captor Belligerent Party may pos-sess information according to which the goods will eventually be transported from neutral to enemy con-trolled territory. In such cases, the initial destination is irrelevant. The legality of the capture will eventually be the determined by a prize court.
6. The concept of contraband is limited to goods destined for territory under the control of the enemy and it does not apply to exports from enemy territory. Goods exported from enemy territory do not qualify as contraband. The only lawful way of interfering with enemy exports aboard neutral civilian aircraft is by es-tablishing and enforcing a blockade (for aerial blockade, see Section V).
7. It is immaterial whether the pilot, the aircrew, the owner or the operator of the aircraft knows that the cargo is contraband.

712. Art. 53 (h) of the HRAW, see fn. 710.
713. Para. 153 (a) of SRM/ACS, see fn. 711.
714. Para. 149 of SRM/ACS: “In order to exercise the right of capture …, the belligerent must have published contraband lists. The precise nature of a belligerent’s contraband list may vary according to the particular circumstances of the armed conflict. Contraband lists shall be reasonably specific.”

1. Rule 140 (b) is based on Para. 153 (b) of the SRM/ACS.^[715] See also Art. 45 (1) of the 1909 London Declaration.^[716]
2. It is a well-established belligerent right to prevent neutral civilian aircraft from transporting enemy troops. It must be stressed, however, that the incidental presence on board of some enemy nationals who are members of the armed forces or who are going to enlist does not justify capture as prize. Therefore, the flight must be undertaken “especially” for that purpose.

715. Para. 153 (b) of SRM/ACS, see fn. 711.
716. Art. 45 (1) of the 1909 London Declaration, see fn. 709.

1. Rule 140 (c) is based on Art. 46 (2) of the 1909 London Declaration.^[717]
2. Neutral civilian aircraft “operating directly under enemy control, orders, charter, employment or direction” lose their neutral character. Then, they may be assimilated to enemy civilian aircraft that, according to Rule 134, are always liable to capture as prize.

717. Art. 46 of the 1909 London Declaration: “A neutral vessel will be condemned and, in a general way, receive the same treatment as would be applicable to her if she were an enemy merchant vessel: (1) if she takes a direct part in the hostilities; (2) if she is under the orders or control of an agent placed on board by the enemy Government; (3) if she is in the exclusive employment of the enemy Government; (4) if she is exclusively engaged at the time either in the transport of enemy troops or in the transmission of intelligence in the interest of the enemy. In the cases covered by the present Article, goods belonging to the owner of the vessel are likewise liable to condemnation.”

1. According to Art. 53 (f) of HRAW,^[718] a neutral civilian aircraft is liable to capture as prize if it “has no papers or insufficient or irregular papers”.
2. Para. 153 of the SRM/ACS states that [n]eutral civil aircraft are subject to capture outside neutral airspace if they are engaged in any of the activities in Para. 70 or if it is determined as a result of visit and search or by any other means, that they … (d) present irregular or fraudulent documents, lack necessary documents, or destroy, deface or conceal documents.”
3. The lack of papers or the presentation of irregular or fraudulent papers is sufficient ground for suspicion that the aircraft has in fact enemy character and that it is, thus, subject to capture as prize.
4. According to Art. 54 of the HRAW, the “papers of a private aircraft will be regarded as insufficient or irregular if they do not establish the nationality of the aircraft and indicate the names and nationality of the crew and passengers, the points of departure and destination of the flight, together with the particulars of the cargo and the conditions under which it is transported. The logs must also be included.”

718. Art. 53 (h) of HRAW, see fn. 710.

1. This Rule is based on Art. 53 (b) of the HRAW^[719] and on Para. 153 (e) of the SRM/ACS.^[720]
2. In the immediate area of military operations (see Rule 106 (a)), Belligerent Parties enjoy the right to prevent the passing of neutral civilian aircraft if their presence is “likely to prejudice the success of the operations”.^[721] Not complying with such belligerent orders, renders the neutral civilian aircraft liable to capture as prize.

719. Art. 53 (b) of HRAW, see fn. 710.
720. Para. 153 (e) of SRM/ACS, see fn. 711.
721. Art. 30 of the HRAW: “In case a belligerent commanding officer considers that the presence of aircraft is likely to prejudice the success of the operations in which he is engaged at the moment, he may prohibit the passing of neutral aircraft in the immediate vicinity of his forces or may oblige them to follow a particular route. A neutral aircraft which does not conform to such directions, of which he has had notice issued by the belligerent commanding officer, may be fired upon.”

1. According to Art. 53 (i) of the HRAW,^[722] a neutral civilian aircraft is liable to capture as prize if it “is engaged in breach of a blockade duly established and effectively maintained”. See also Para. 153 (f) of the SRM/ACS.^[723]
2. If a Belligerent Party has established an aerial blockade, and if that aerial blockade meets the requirement of effectiveness, that Belligerent Party is entitled (and, in fact, expected) to prevent all aircraft from entering or leaving the blockaded area (see Rule 151 and Rule 154).

722. Art. 53 (i) of HRAW, see fn. 710.
723. Para. 153 (f) of SRM/ACS, see fn. 711.

Rule 141 reaffirms the traditional principle “free ship − free goods”^[724] (which is also applicable to aircraft) from which one can deduce that cargos on board neutral civilian aircraft are exempt from capture as prize. However, there are two exceptions to this principle. These two exceptions are listed in Rule 141 (a) and in Rule 141 (b).^[725]

724. Para. 2 and Para. 3 of the 1856 Paris Declaration: “(2) The neutral flag covers enemy’s goods, with the exception of contraband of war. (3) Neutral goods, with the exception of contraband of war, are not liable to capture under enemy’s flag.”
725. Para. 154 of the SRM/ACS: “Goods on board neutral civil aircraft are subject to capture only if they are contraband.”

1. When the goods on board a neutral civilian aircraft constitute contraband, they may be captured as prize. This is the legal position, notwithstanding the fact that the aircraft — being neutral — must be released after inspection.
2. Traditionally, if contraband goods on board a vessel (and, presumably, also an aircraft) form more than half the cargo,^[726] the neutral vessel (and aircraft) may itself be captured as prize.

726. Art. 40 of the 1909 London Declaration: “A vessel carrying contraband may be condemned if the contraband, reckoned either by value, weight, volume, or freight, forms more than half the cargo.”

1. According to Section E and Rule 174, a neutral civilian aircraft becomes a military objective and thus liable to attack, if it engages in activities making an effective contribution to the enemy’s military action.
2. In such cases, the cargo shares the legal status of the aircraft. If the aircraft is not attacked but merely captured (see Rule 140), its cargo may be captured as well, and this irrespective of its standing as contra-band.

1. Any interference with neutral civilian aircraft and goods on board can only take place outside neutral territory.
2. The capture as prize of neutral civilian aircraft can only take place in accordance with Rule 140.
3. The capture as prize of goods on board neutral civilian aircraft can only take place in accordance with Rule 141.
4. In all cases, the validity of capture as prize must be adjudicated by a prize court.
5. It follows from Rule 142 that, if no prize court exists, there is no way for a Belligerent Party to enforce its entitlements under Rule 140 and Rule 141. Hence, if it wishes to condemn neutral civilian aircraft and goods on board, it has no choice but to set up such courts.