Related Rule
South Africa
Practice Relating to Rule 85. The Use of Incendiary Weapons against Combatants
South Africa’s LOAC Teaching Manual (2008) states:
3. Means and Methods of Warfare
Several specific weapons are governed by specific treaties. These treaties establish two categories of weapons, to wit[:]
- Weapons of which the use is totally prohibited; and
- Weapons of which the use is permitted under certain conditions.
Weapons of which the use is Permitted under Certain Conditions:
- Incendiary Weapons (Geneva Protocol III on Prohibitions or Restrictions on the Use of Incendiary Weapons dated 10 October 1980)
Definition.
“Incendiary weapon” means any weapon or munition which is primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat or a combination thereof, produced by a chemical reaction of a substance delivered on the target.
- Examples. Incendiary weapons can take the form of flamethrowers, shells, rockets, grenades, mines, bombs or other containers of incendiary substances (also Napalm, phosphorous bombs).
- The following are not considered to be incendiary weapons:
- Munitions which may have incidental incendiary effects, such as illuminants[,] tracers, smoke or signalling systems; or
- Munitions designed to combine penetration, blast or fragmentation effects with an additional incendiary effect, such as armour[-]piercing projectiles, fragmentation shells, explosive bombs and similar combined effects munitions in which the incendiary effect is not specifically designed to cause burn injury to persons, but to be used against military objectives such as armoured vehicles, aircraft and installations or facilities.
- Conditions for Permitted Use (Geneva Protocol III Article 2):
[-] Incendiary weapons which are not air delivered may be used[:]
- When the military objective is clearly separated from any concentration of civilian persons; and
- Subject to precautions to limit incendiary effects to the military objective when the tactical situation permits. 
South Africa, Advanced Law of Armed Conflict Teaching Manual, School of Military Justice, 1 April 2008, as amended to 25 October 2013, Learning Unit 3, pp. 174, 176 and 178–179.
[emphasis in original]
The manual further states:
Targeting Considerations and Means and Methods of Air Warfare
- During armed conflict, enemy military aircraft and missiles may be attacked and destroyed in airspace anywhere outside of neutral jurisdiction.
- Attack against aircraft may be made by any method or weapon, not otherwise prohibited, including air-to-air or ground-to-air missiles, and explosive or incendiary projectiles.
- The use of incendiary projectiles, limited in some uses on land, was expressly recognised as not prohibited against aircraft by the 1923 Draft Hague Rules of Air Warfare. 
South Africa, Advanced Law of Armed Conflict Teaching Manual, School of Military Justice, 1 April 2008, as amended to 25 October 2013, Learning Unit 4, pp. 217–218.