I typically bring my laptop on the plane to use for working or watching a DVD. I don’t like to be interrupted by losing my battery mid flight. Here are some of my best practices for getting the most out of my laptop battery:

1. Make sure the laptop batteries are charged before going to the airport. Don’t necessarily count on finding AC power at the airport to take care of this. You may also not have time at the airport to fully charge a dead battery. Trickle charges can take a few hours.
2. Arrive early enough to find one of the few AC outlets at the gate. Top off the charge on your batteries before boarding the plane. AC outlets are often tucked away along the windows, in the floor, built into vertical support beams. If you can’t find an available outlet at your gate, go to the gate across the hall or to the next gate over and look for an AC outlet you can use there while still within earshot range of the boarding calls at your gate. I’ve also seen outlets in airport restaurants – relax, have some food, charge your laptop.
3. If you’re going to use the laptop while waiting at the gate, make sure it’s on AC power instead of using batteries.
4. Before boarding the plane, put the laptop in suspend mode instead of shutting it down. When you power the laptop back on when seated on the plane, the laptop comes up instantly in the OS rather than chewing up battery during a 5-10 minute boot up process
5. Limit the use of USB devices, CD-ROM, and DVD-ROM. These peripherals chew up battery at a fast rate.
6. Limit the use of disk intense applications such as defrag or virus scan. This also chews up batteries at a fast rate.
7. Limit the use of processor intense applications which will cause the CPU and fans to draw more power.
8. Run the display at the dimmest setting possible.
9. Turn off the Wireless and Blue tooth radio.
10. Bring an extra travel battery that is obviously already charged. The last couple of laptops I’ve had I had the extra travel battery installed along with the regular battery at the same time. It makes the laptop a little bulkier and heavier, but for me the extended battery time (5-6+ hours) is worth it.
11. When you’re done using the laptop on board the plane, if you’re critically low on battery, shut down the OS or hibernate as opposed to putting it into suspend mode. Suspend mode still draws minimal amounts of power and critical bits may still be active in RAM. If you go into suspend and then the laptop battery dies completely, the plug/power will have been basically been pulled from the OS and you’ll lose any unsaved information you were actively working on. It’s just plain not good to yank the power from your computer.