I'm quite well-endowed and prefer underwire bras for support (and comfort, ironically...) But when I do overnight flights, I do wear a non-underwire bra. Lately I've been wearing the Bali "downtime cool stretch" bra -
http://www.barenecessities.com/bali-...pf_id=Bali3375
I don't like it as much as underwire in general, but it's great for flights. Sports bras are too confining, shelf bras are useless- this is a nice middle ground for me. And I can find them cheap on sale at Kohls.....