I just did a redeye the other day. I agree with all of the suggestions so far - but I always take a hefty dose of Tylenol PM. I wouldn't suggest trying this for the first time on a flight...but it always gets me to sleep - and I am never groggy when I wake up (even as short as 4 hrs).

The only caution I have is that if you aren't able to get to sleep within 45 mins of taking the pill - then wait to take it. I find that if I'm not able to get to sleep within 45 mins of taking it ... that it doesn't help me get to sleep at all.

Good Luck!
Chris