If I'm going to Asia (where timing your sleep to accommodate the destination time zone is vital for workday survival) I rely on a nice mix of red wine and a xanax. I'm scared of "sleeping" pills like ambien - 36k ft is not where I want to be doing random things I can't remember.

When flying with my kids (8 & 10) dramamine is a lifesaver.

(disclaimer that this is my recipe - use at your own risk and always test these on the ground!)