CHICAGO -- It's easier than ever for airborne travelers to file reports to the office, send faxes or even cruise the Internet from a laptop plugged into an onboard phone -- easy, that is, if the battery works.


That raises the question of why aircraft are not equipped with electrical sockets.


Skyguide, the pocket airline schedule published by American Express in the United States, this month asked that question.


"If the airline wanted to do that, we'd have to install a frequency converter so it could convert the airplane's power, which is about 400 hertz, to 60 hertz -- the typical power requirement for household appliances," the guide quoted a Boeing spokesman as saying.


"It's fairly expensive to do, and maybe that's why airlines simply haven't asked us for it," Boeing added.


A spokeswoman for American Airlines added that beyond the conversion problem, "there's only a limited amount of energy produced and it's for aircraft needs. We'd have to rewire all the airplanes and then there's a question of whether we'd have to charge for the use."


Rich Malloy, editor of Mobile Office Magazine, says another hindrance is that airlines are afraid a passenger might plug in a hair dryer or some other high-power appliance and zap the power system. So don't look for an AC plug any time soon.


But what about better batteries? Malloy says battery life for laptops and notebooks "is improving, but kind of slowly. The big improvement is lithium-ion batteries," which are becoming more common.