[GuerraCivil]

Well, to put it in analysis:

1) Japanese: attacking parachuting enemies was a systematic practice endorsed by the doctrine of "aerial extermination action". The so-called Bushido code with "no mercy, no prisoners" attitude played also a part, but it was a secondary motive. Most important was the doctrine of "aerial extermination action" which considered enemy pilots as an enemy asset to be eliminated whenever possible.

2) Americans: attacking parachutig enemies often, but probably not a systematic practice as much as with Japanese.

3) Germans: at the Western front individual cases, at the Eastern front quite common practice but perhaps not as systematic as it was by Japanese. The nature of warfare at the German Eastern Front was more ruthless than at the Western Front, because ideological hate propaganda of both sides was more strong and demonised the enemy much more. One German officer described the Western Front being a "waiting room for hell" whereas the Eastern Front was the hell itself.

4) British/Commonwealth pilots: seems not to have been systematic practice, but individual cases existed.

5) Others: Polish - motivated by the revenge spirit to make frequent attacks? Italians - not known cases as far as I know.

But difficult to tell when it comes to individual cases - anyone can have a moment of anger which will lead to action to be regretted later and not repeated after second thoughts. To some other person it is maybe just the crossing of the decisive line after which the similar action is repeated always when given a chance.

One should also make a difference between parachuting paratroopers and parachuting pilots when they have been shot from the ground. The former are "fair game" as it makes reason to eliminate them well before they get to the ground and take armed organized action. The parachuting enemy pilot is not so much threat - he is a individual combatant knocked out of air combat and can be taken as a POW without much difficulty.