I can kill hours with games on my laptop. Sims 2 mostly, but Unravel (I think you need an xbox controller) and 2pointhospital are also good
Audiobooks on an ipod make time go faster. I find 'Wedding night' by Sophie Kinsella funny, which passes the time more quickly
Crosswords? Not very thrilling but it would kill some time
Challenge yourself to learning a new language, or practicing one
Join the mile high club with a total stranger
Take a box of face paints, a hand mirror and some makeup remover wipes and go nuts! You could charge desperate parents looking for entertainment for their children too
Make a list of all the songs you can think of with the word 'Baby' in. Buy yourself a present when you land if you get to more than 100. You can ask other passengers and flight staff for input if you like
Look around at the other passengers and assign names, ages, families, professions, hobbies and deep dark secrets to each individual. Keep track of them in a little notebook
Take a rubiks cube
Pretend you're an air marshal (do we have them in the UK?) or an undercover airline inspector
Write poetry. It can be about absolutely anything, and it doesn't matter how shit it is, but the challenge is it has to rhyme. See how long you can keep one poem going for
Dope yourself up. I hear Nightnurse is good!! Maybe not if you're hiring a car at the other end though...
Get chatting to the person sitting next to you. Make up a ludicrous life for yourself and see how far you can push it and have them still believe you
Do a jigsaw puzzle
Pull terrible faces at any kids nearby without their parents noticing. Look shocked and horrified when they make faces back, and mutter things about 'Children today!' while their parents tell them off
Invent a brand new dance style with some serious moves (maybe best in your head and don't actually practice it until you get off, unless there's plenty of room in the aisle)
Play cats cradle
Write a short story
Take a deck of cards and play solitaire
Ask the cabin crew if you're nearly there yet at frequent intervals. See how long it takes for them to get pissy with you
Take an old pair of socks and some craft bits and make sock puppets. Sticky back velcro dots might work if you're not allowed to take glue as hand luggage
Make detailed plans on what you'll do when you rule the world
Write a new Friends episode. It can be interjected inbetween a couple of the old good ones, it doesn't have to follow on from the end of season 10, unless you want it to
Print off a bunch of old year 6 SATS maths papers to take with you. See how well you do on them
Take a mini magnetic chess board and practice your game
Do adult colouring. Just how 'adult' is up to you!
Plan a party down to the smallest details. Think of a theme, what you'll wear, what food and drinks you'll provide, what entertainment there'll be, who you'll invite, all of it!
Make little models out of plasticine
Buy the original 'Find it' and well, find everything!
Draw your dream home
Practice meditation
Pretend you have 17 pets. Imagine what they might be, what their names are, their personalities, favorite toys, how you would keep them all happy etc
Learn cross-stitch
Eat snacks, but always with both hands behind your back
There, if that lot doesn't keep you occupied for 7 hours I don't know what will!!