Very fragile in AH though 
Due to size as discussed in the recent Yak-9U vs Yak-3 thread. Shots on big aircraft are more likely to concentrate on the same "damage area" whereas on a small fighter the same spread of rounds hits multiple "damage areas". As an example using made up numbers, burst that does 10 damage to a Mossie's inner right wing and 2 damage to its fuselage, neatly removing the right wing by exceeding its 9 damage value threshold may well not kill a Yak-3 when centered on the Yak's inner right wing because it might do 3 points to the Yak's inner right wing, 2 points to the outer right wing, 2 points to the center fuselage, 2 points to the inner left wing and the rest that hit the Mossie miss entirely, leaving the Yak to fly off apparently unhurt because the 3 damage to its inner right wing didn't exceed the Yak's inner wing value of 4. The Mossie's inner right wing is just so much larger in area that it causes damage to be tracked in a focused manner.
This is an artifact of AH simple damage model. The solutions that I see would be either a much more detailed damage model, something that is prohibitively difficult, or making damage area's as uniform in size as possible across aircraft, meaning that a B-29 would have many, many more damage areas than an I-16. Both would require major overhauls of the damage model and perhaps graphics.
