Bring an extra power pack.
You want to be safe, and you won't be sorry that you were. Flying makes for extremely long days and a lot of boredom. Boredom that leads to you texting, calling people, snapchatting and checking scores excessively. Boredome that leads to drained batteries, essentially. So, when you're stuck on the tarmac, and your phone dies, pull one of these puppies out and enjoy the extra juice.