I can't sleep for more than 30 minutes or so on a plane. After that, I'm awake for the duration of the flight, no matter how long it is. I wonder if this neck-propper-upper would help?
Enter the UpRight Sleeper, a neck support that makes snoozing upright more comfortable (plus way cooler looking!). $40 takes one home, but the VERY fashionable cover costs $10 extra. I prefer the no-cover model because I'm hoping a flight attendant mistakes me for someone with a debilitating neck injury and moves me up to first class.
Here's the website for the UpRight Sleeper. But watch out -- it has a video that starts playing right away, and that narrator's voice is booming.
Geekologie: Finally, A Decent Neck-Rest For Sleeping Upright