This was just brought up by someone else too. They bought a 2nd tier plane and could not always access it in the hangar.
[NLR] McFate wrote: It is probably still there.
Keep in mind that there are 2 sets of hangars. One side is all the German planes, the other is the Allied planes. You only have access to one or the other in each game. As you buy new planes and upgrades you will need to get planes for both.
The same thing happens to a lot of new players. Check it out in game. If something else is going on post again.