Aircraft in general lack armor.
You might find some like the A-10 that have a titanium tub that the pilot sits in, otherwise it’s all aluminum and isn’t stopping anything spicier than a pistol.
WW2 and Cold War aircraft might have had something like a single steel plate behind the pilot or bulletproof glass but that’s the extent of it. You could walk up to a helicopter and push a screwdriver through the skin, bullets will deviate at most, not stop until they hit some mechanical components like the engine
Combat aircraft survive by avoiding fire or having redundant systems, not by deflecting hits. Aircraft can’t be heavy and you can’t be light enough to fly AND fully armored.
Latest Answers