Asus Eee PC1000HE
If you're on a budget, the Asus Eee PC1000HE netbook might be the way to go; I've seen it online for and . Asus claims the netbook can run for up to 9.5 hours on one charge. That's far above the average netbook, which usually lasts only about 2 to 3 hours per charge.
The Wrap Up
If you frequently fly on long-haul international flights without acess to a power port, the HP or Dell machines might be worth considering. Otherwise, your best bets are either the ThinkPad X200 or, if money's tight, the Asus Eee PC1000HE.
And if you're a Mac fan, consider the new 17-inch MacBook Pro. Its battery, which isn't user-removable, is said to last up to 8 hours on a single charge. .