I carry both Ambien (Stilnoct, as it's called in Europe) and Sonata in my travel kit, and typically use Sonata for flights of six hours or less (east coast transatlantics).

I generally find that Ambien is slightly quicker acting, and is more effective at keeping me asleep, but Sonata does the trick for shorter flights without a hangover.

Having been the victim of amensia while taking Ambien on a short flight, I can assure you it is a scary experience I would not want to repeat. These days, I'm very very careful about what I take and how much sleep I'll be able to get.