Laptops are the best thing that ever happened to airline travel. They enable you to catch up on your work, play games or watch a movie while you are traveling.

Better still, many airlines are now installing costly equipment that enables you to access the Internet during flights. Most of these systems use your laptop's built-in Wi-Fi to connect.

Unfortunately, this laptops-in-the-sky nirvana probably won't last. The problem: Laptop batteries can explode catastrophically. It's happened before, and it will happen again. It's only a matter of time before it happens in-flight.

The FAA forbids you to use your iPod during takeoff — do you think it won't ban laptop batteries?

What's so bad about laptop fires?

Laptop batteries are typically plastic and metal containers that contain somewhere between six and nine individual lithium-ion cells, which look a little like AA batteries. If any of these gets too hot — around 350 degrees for legitimate, noncounterfeit batteries — they can leak flammable liquid, then explode, causing a chain reaction through the rest of the cells (a process called thermal runaway). The temperature increases and quickly melts a hole in the laptop. As additional cells explode, flaming, poisonous liquid can be thrown several feet in any direction. These explosions and flames are accompanied by acrid, toxic smoke.

The reaction on a crowded airplane to multiple explosions, flames and toxic smoke could easily be panic. People would get up out of their seats and move down the aisles, blocking the path of flight attendants trying to extinguish the flames with on-board extinguishers. The rush of passengers to the front or back of the plane could affect the pilots' weight-and-balance calculations. And the FAA itself admits that airline crews are ill-prepared to handle battery fires in-flight.

Another risk is that terrorists could board a plane with a large number of laptop batteries, both in laptops and in laptop bags as "spares." During flight, they could combine all laptop batteries into a single unit, then heat them up to create explosions, fire, panic and, possibly, damage to the airplane.

What the ban would look like

New rules came into effect Jan. 1 that ban spare laptop batteries in checked luggage. Batteries actually installed inside devices are allowed, and most spare batteries in your carry-on are fine, too. But carry-on batteries are now governed by a complicated new set of rules.

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