Rule 27

Without prejudice to Sections I, J and L of this Manual, the following activities may render any other enemy aircraft a military objective:

[Commentary]

(a) Engaging in hostile actions in support of the enemy, e.g. intercepting or attacking other aircraft; attacking persons or objects on land or sea; being used as a means of attack; engaging in electronic warfare; or providing targeting information to enemy forces.

[Commentary]

(b) Facilitating the military actions of the enemy’s armed forces, e.g., transporting troops, carrying military materials, or refuelling military aircraft.

[Commentary]

(c) Being incorporated into or assisting the enemy’s intelligence gathering system, e.g., engaging in reconnaissance, early warning, surveillance or command, control and communications missions.

[Commentary]

(d) Refusing to comply with the orders of military authorities, including instructions for landing, inspection and possible capture, or clearly resisting interception.

[Commentary]

(e) Otherwise making an effective contribution to military action.

[Commentary]

  1. This Rule is based on the SRM/ACS.[264] See also Para. 8.8 of NWP[265] and Paras. 12.36 and 12.37 of the UK Manual.[266]

  2. The crux of Rule 27 is qualification as a military objective. In this regard, it is not necessary that the aircraft in question be conducting an attack (see Rule 1 (e)). Instead, it need only be making an effective contribution to the enemy’s military action and its destruction, capture or neutralization would yield a definite military advantage in the circumstances ruling at the time (see Rule 1 (y)). For instance, a State aircraft — not qualifying as a military aircraft — passively gathering intelligence or conducting electronic warfare that merely interferes with enemy communications is not “attacking” but its actions still render it a military objective.

  3. Any attack on such aircraft must comply with all elements of Section D (see especially Rule 14) and Section G, in particular Section G (III) pertaining to specifics of attacks directed against aircraft in the air.

  4. While all enemy aircraft other than enemy military aircraft may lose their protection, it needs to be stressed that civilian aircraft, medical aircraft, civilian airliners and aircraft granted safe conduct do not lose their protection unless certain conditions are met. These conditions are set out, respectively, in Section I, Section L, and Section J.

  5. The following activities relate both to intended future use (“purpose”) and to “use”, and are therefore subject to the application of Rule 22 (c) and 22 (d).

  6. Rule 27 does not apply to civilian airliners, which are dealt with in Rule 63.

  7. For enemy civilian aircraft, see also Rule 50.

  8. Rule 27 applies only to enemy aircraft. Neutral civilian aircraft are dealt with in Rule 174.

  1. Para. 63 of the SRM/ACS: “The following activities may render enemy civil aircraft military objectives: (a) engaging in acts of war on behalf of the enemy, e.g., laying mines, minesweeping, laying or monitoring acoustic sensors, engaging in electronic warfare, intercepting or attacking other civil aircraft, or providing targeting information to enemy forces; (b) acting as an auxiliary aircraft to an enemy’s armed forces, e.g., transporting troops or military cargo, or refuelling military aircraft; (c) being incorporated into or assisting the enemy’s intelligence-gathering system, e.g., engaging in reconnaissance, early warning, surveillance, or command, control and communications missions; (d) flying under the protection of accompanying enemy warships or military aircraft; (e) refusing an order to identify itself, divert from its track, or proceed for visit and search to a belligerent airfield that is safe for the type of aircraft involved and reasonably accessible, or operating fire control equipment that could reasonably be construed to be part of an aircraft weapon system, or on being intercepted clearly manoeuvring to attack the intercepting belligerent military aircraft; (f) being armed with air-to-air or air-to-surface weapons; or (g) otherwise making an effective contribution to military action.”

  2. Para. 8.8 of NWP (“Air Warfare at Sea”): “Enemy merchant vessels and civil aircraft may be attacked and destroyed by military aircraft only under the following circumstances: 1. When persistently refusing to comply with directions from the intercepting aircraft; 2. When sailing under convoy of enemy warships or military aircraft; 3. When armed with systems or weapons beyond that required for self-defense against terrorism, piracy, or like threats; 4. When incorporated into or assisting in any way the enemy’s military intelligence system; 5. When acting in any capacity as a naval or military auxiliary to an enemy’s armed forces; 6. When otherwise integrated into the enemy’s war-fighting or war-sustaining effort.”

  3. Para. 12.36 of the UK Manual: “Enemy civil aircraft may only be attacked if they meet the definition of a military objective in paragraph 5.4.1.”
    Para. 12.37 of the UK Manual: “The following activities may render enemy civil aircraft military objectives: (a) engaging in acts of war on behalf of the enemy, eg, laying mines, minesweeping, laying or monitoring sensors, engaging in electronic warfare, intercepting or attacking other civil aircraft, or providing targeting information to enemy forces; (b) acting as an auxiliary aircraft to an enemy’s armed forces, eg, transporting troops or military cargo, or refuelling military aircraft; (c) being incorporated into or assisting the enemy’s intelligence gathering system, eg, engaging in reconnaissance, early warning, surveillance, or command, control, and communication missions; (d) flying under the protection of accompanying enemy warships or military aircraft; (e) refusing an order to identify itself, divert from its track, or proceed for visit and search to a belligerent aircraft that is safe for the type of aircraft involved and reasonably accessible, or operating fire control equipment that could reasonably be construed to be part of an aircraft weapon system, or on being intercepted clearly manoeuvring to attack the intercepting belligerent military aircraft; (f) being armed with air-to-air or air-to-surface weapons; or (g) otherwise making an effective contribution to military action.”

  1. Rule 27 (a) sets forth the most definitive example of aircraft becoming military objectives through purpose or use (see Rule 22 (c) and on 22 (d)).

  2. The phrase “hostile actions” refers to actions that typically are conducted by military aircraft during, and in connection with, hostilities. Such activities are not limited to attacks, but would also include, for instance, intelligence gathering, surveillance and reconnaissance activities.

  3. “Hostile actions” need not be directed against the military forces or assets. As long as there is a nexus to the armed conflict, such acts are liable to be committed against civilians, the civilian population or even objects within one’s own territory, regardless of whether the object is of a military or civilian nature or whether the action is lawful or not.

  4. The phrase “in support of the enemy” is included to emphasize that there must be a nexus with the conflict, in other words, that the act in question must be intended to benefit the enemy. This criterion would distinguish a hostile action from a purely criminal act.

  5. “Targeting information” is any information that enables an attack to be conducted. Examples include information pertaining to the location of the target, target area defences, description of the target area, and identification of reference points that identify the target. The acquisition and transmission of targeting information may be carried out by civilian aircraft with sensors used for civilian purposes (such as search-and-rescue aircraft equipped with infrared sensors) or may simply involve passing information as to what the aircrews observe. Such activities will constitute a hostile action in support of the enemy.

  6. It is not necessary that the enemy directed or even invited or endorsed the act in question to occur. What counts is the intent of the actor engaging in it, together with the fact that the act is of a nature to support the enemy, which determines whether a nexus to the armed conflict is present.

  7. The reference to aircraft “used as a means of attack” is specifically included to cover a situation where a civilian aircraft is flown into the intended target. In such cases, the aircraft effectively becomes a means of warfare, that is, a weapon. Military aircraft used for this purpose, such as those employed in the Japanese Kamikaze attacks of WWII, already qualify as military objectives by nature. As for (hijacked) civilian airliners, see Rule 63.

  8. The use of any aircraft other than a military aircraft as a means of attack is prohibited at all times, see Rule 115 (b).

  9. State aircraft that are not military aircraft are not entitled to exercise belligerent rights (such as conducting attacks) (see Rule 17) and, as a rule, are not military objectives by nature. However, when under the exclusive control of the armed forces and being used for military purposes, such aircraft qualify as military objectives under Rule 27 (a) or under Rule (b). Hence, they may be attacked for so long as they are so used.

  10. Rule 27 (a) applies also in non-international armed conflict.

  1. The examples set forth in Rule 27 (b) are merely illustrative. For instance, being armed with air-to-air or air-to-surface missiles exposes any aircraft to attack because there are no civilian purposes attendant to such arming. In every case, the essential inquiry is whether the aircraft in question has become a military objective through use or purpose.

  2. Rule 27 (b) is included to make clear that aircraft need not be engaging in “attacks” to qualify as a military objective. The requirement is that their actions make an effective contribution to the enemy’s military actions. The phrase “military actions” has been intentionally employed to exclude activities that are more general in character, e.g., general support to the enemy’s war effort. An example of facilitation of military action will be the carrying of ammunition for use by military units. The key is that a clear nexus exists between the flight and military actions of the enemy.

  3. Rule 27 (b) applies also in non-international armed conflict.

  1. Rule 27 (c) is based on the second sentence of Art. 16 of the HRAW.[267]

  2. “Incorporat[ion]” means that the aircraft is an integrated part of the enemy’s intelligence gathering system. This could for instance occur if an aircraft the primary function of which is environmental monitoring of the EEZ, routinely reports the presence of foreign warships, thus relieving the workload of military maritime patrol aircraft. The essence of incorporation is that the activity in question is regular or systematic and the enemy relies on the information provided in calculating its actions, thereby relieving it of the need to gather such information itself. “Assisting” means providing assistance to the enemy without necessarily being an integrated part of its intelligence gathering-system.

  3. Rule 27 (c) differs from that set forth in Rule 27 (a) regarding the provision of targeting information. In Rule 27 (c), the intent is to address activities that are integrated into the enemy’s intelligence gathering system (incorporation) or in which the armed forces obtain assistance for a particular operation (assistance), as distinct from those in which the aircraft merely happens to acquire information that it then passes on to the military which uses it for targeting purposes. In other words, Rule 27 (a) refers to incidental provision of such information, whereas Rule 27 (c) addresses planned activities.

  4. The characterization of an activity as intelligence gathering must be made carefully. Information acquired in the course of normal flights operated by other than military aircraft may be of value to enemy forces. For instance, information regarding weather, the proximity of other aircraft, and communications with other aircraft or ground control may all be militarily useful. However, reporting such information through normal aviation channels, even if it ends up in the hands of the military, does not constitute intelligence gathering. Intelligence gathering is limited to the intentional collection of information for military purposes.

  5. Rule 27 (c) applies also in non-international armed conflict.

  1. Art. 16 of the HRAW, see fn. 246.

  1. Rule 27 (d) is reflective of Para. 62 (e) of the SRM/ACS.[268] It addresses the situation where military forces encounter an enemy aircraft other than a military aircraft that is not clearly engaging in activities qualifying it as a military objective. When this situation occurs, the military forces are entitled to order that aircraft to identify itself and its activities. If necessary, the aircraft can be ordered to land for inspection (see Rule 134). In certain situations (see Section U (I)), the aircraft may be captured as prize. It may also be diverted from the area of military operations. Refusal to comply with orders to land or clearly resisting interception may render the aircraft a military objective.

  2. When an enemy aircraft other than a military aircraft is “escorted” by enemy military aircraft or warships, in either international airspace or the airspace of Belligerent Parties, they will be presumed to refuse to comply with the orders of military authorities.[269] The presumption is rebuttable because the attendant circumstances may indicate to an attacker that the escorted aircraft will in fact comply. For instance, the flight commander may communicate to an intercepting aircraft his intention to comply. Of course, the escorting military aircraft or warships are military objectives by nature.

  1. Para. 62 (e) of SRM/ACS: “Enemy civil aircraft may only be attacked if they meet the definition of a military objective in paragraph 40: … (e) refusing an order to identify itself, divert from its track, or proceed for visit and search to a belligerent airfield that is safe for the type of aircraft involved and reasonably accessible, or operating fire control equipment that could reasonably be construed to be part of an aircraft weapon system, or on being intercepted clearly manoeuvring to attack the intercepting belligerent military aircraft.”

  2. Para. 63.3 of the Commentary on the SRM/ACS: “Subparagraph (d) is similar to paragraph 60 (d) which includes sailing under convoy of enemy warships or military aircraft, an activity that may render an enemy merchant vessel a military objective. An enemy civil aircraft that flies under the protection of accompanying enemy warships or military aircraft places itself at risk in the immediate area of hostilities since the enemy warships or military aircraft are military objectives. Belligerent forces might assume that the protected enemy civil aircraft is acting as an auxiliary aircraft to the enemy’s armed forces, or, in pressing an attack, belligerent forces may misidentify the enemy civil aircraft.”

  1. This is a “catch-all” provision designed to emphasize that the activities which render an enemy aircraft other than a military aircraft subject to attack are not necessarily limited to the examples given in Rule 27 (a)–(d).

  2. The key is (intending to) engaging in any activity that would meet the criteria set forth for a military objective, i.e. (i) making an effective contribution to the enemy’s military action; and (ii) its destruction, capture or neutralization would yield a definite military advantage for the attacker in the circumstances ruling at the time (see Rule 1 (y) and Rule 22).

Categories: E: Specifics of Air or Missile Operations