It's happened to many an entrepreneur. You board a five-hour flight from, say San Francisco to New York, with plans to finish the stack of work tucked into your laptop case. An airplane is often a great place to be productive, thanks to the absence of nagging colleagues, e-mail, ringing phones, memos, and faxes at 30,000 feet -- provided the technology you need is in working order

Sometimes, you barely make it over South Dakota before your computer warns you it's about to "hibernate" as you're battery power is at just five percent. Now how exactly do you plan to finish that sales report before you land?

Energy management has been a problem since the earliest days of mobile computing. Drains on a battery include virtually every component on your laptop, including the screen, the hard drive, the CD-ROM and DVD-ROM, and other peripherals. The biggest culprit? DVD movies, which cause the screen to run at full power for the life of the movie.

Unfortunately, there is no magic-bullet solution. But there is something you can do aside from lugging a spare battery. The following are a few tips for squeezing more juice out of your laptop:

Dim the lights

You'll certainly need to see your screen, but just how bright do you need it to be? Screens lighted at full strength eat up 15 percent more battery life than if your battery was at 50 percent brightness, says Dell. So, be sure to squeeze more life out of your laptop by reducing the brightness of your monitor a great deal.

Limit your entertainment

The battery will drain faster if there's a spinning disc in your CD-ROM or DVD-ROM drive, such as a game, music CD or DVD movie. Some games offer you the choice to install to the hard drive, so choose this option, as you'll get more life out of your laptop than using the CD-ROM or DVD player, which are massive battery consumers. With other entertainment, your best power value is to work from the hard drive.

Unplug everything

Make sure you have no devices plugged into the laptop that can drain its power, such as a Webcam, USB thumb-stick, or wireless PC card. According to Dell, connected peripherals can impact battery life by up to 12 percent (depending on the peripheral), so get used to the touchpad instead of using an external mouse when you're away from an electrical outlet. What eats up the most battery power? Wireless connectivity, such as Wi-Fi and WWAN, so be sure to turn this feature off if you don't need it (not an issue for airplanes where this should be turned off).

Reduce power consumption

Camille Alcasid, who runs Westside Websites, a Santa Monica, Calif.-based development firm, recommends changing the "Power Options" found on Windows XP. Users can find it in the Control Panel and use it to manually reduce the power consumption of your laptop. "Typically, you want to be able to work on a spreadsheet or word processing," says Alcasid. "By reducing consumption by a third, you can still use those options and extend your life." You can also set alarms to go off when the battery is about to die (for example, at five percent) so you can safely save your information before powering down.

Charge up

In the better-safe-than-sorry category, it's worth noting that air travelers should make a point of recharging the battery before a flight. Find an electrical outlet while you're waiting for your flight at the gate, a restaurant, or airline lounge.