Here is the proof:
This is a relative comparison done by running the same level, Patrol Mission XIII on Easy, with the planes Eagle SS 108, Sniper S 102, Blitzer SS 122, Patriot S 100, Laserbite SS 140, Defender B 48, and Wraith SS 104.
Brobots were dropped, armor was dropped, no equipment enhancing armor was kept. (However, some aspects are not taken inte account: E.g. Defender has 10 % reduction on incoming fire.) The plane was then flown straight into the first fireball, and a screenshot taken after that. The health bars is shown above after this first hit, together with the value of the planes armor. Then planes are ranked from top to bottom, on how much armor they lost after the hit.
As can be seen, the correspond well to the health bar
But looking at Wraith, things get wrong. Wraith should have received the least damage, except for Eagle in the above chart. But it has actually received more damage than Defender, which only has half of Wraith armor value.
This is what it looked like with Sniper: