Actually, there is a work-around.
Since you get a free aircraft the first time you purchase a hanger provided it isn't the instantly-build hanger you can build when you don't start with base facilities, you can just buy whatever you want during this instant period except the hangers, let an hour pass, and buy a large and small hanger.
However, you won't be able to use the hangers for 6 days, and the aircraft won't be delivered until the hangers are built.
I feel sorry for the folks at Revelstoke. :cry:
Still, an expert commander should be able to recover from whatever chaos the aliens deliver during those 6 days (provided the difficulty level isn't set too high).
I think this bug is related to the bug in which no aircraft can be purchased during the initial base menu.