It's in the original rules... Observers are independent, and are able to fire even if their plane is on fire. (it doesn't make sense here without the full rules, but observers can independently unjam guns and change ammo rounds without requiring the plane performing - if I remember well - a straight move...)
All trademarks or tradenames used in this Web site are the property of their respective owners. Material may not be republished, nor may content or images be mirrored on another server without written permission.