Still regarded as a pretty horrible thing to do though so I would suggest avoiding following in their footsteps.
"Attacking parachutists from aircraft in distress is a war crime under the Protocol I addition to the 1949 Geneva Conventions. Firing on airborne forces who are descending by parachute is not prohibited."
"After World War I, a series of meetings were held at The Hague in 1922–1923. Based on the testimony of First World War pilots, a commission of jurists attempted to codify this practice with the Hague Rules of Air Warfare. Article 20 prescribed that:
When an aircraft has been disabled, the occupants when endeavoring to escape by means of parachute must not be attacked in the course of their descent"