(FORTUNE Magazine) – One of the last remaining refuges from the onslaught of electronic mail is about to disappear. Beginning in late November, Singapore Airlines will test a new system to allow business- and first-class passengers on selected flights between Los Angeles and Singapore to send and receive e-mail and browse popular Websites while cruising above the Pacific.

If all goes according to plan, air travelers next year will be able to stay in touch with the office--and the office will be able to track them down--as airplanes in effect become mobile Internet service providers. Several other airlines are experimenting with two-way data links to aircraft, but Singapore is believed to be the first to start testing space satellites as a way to relay the data, allowing its passengers to get e-mail over the ocean as well as the land.

Here's how the sky mail works:

First- and business-class passengers in Singapore's two test Boeing 747s will be able to bring their laptops aboard, plug into a power outlet in the seat--a special adapter is required, which you'll have to buy in advance--and sign up for the airborne Internet service (pricing has not been set). Disks and CD-ROMs containing the necessary software for Windows or Macintosh computers will be available in the airport and on the plane, says Yap Kim Wah, senior vice president for marketing services.

Each test 747 will have its own server. Just before the plane takes off, the server, using a high-speed Net connection at the airport, sucks down thousands of popular Web pages from such sites as Yahoo, Bloomberg, WSJ.com, Amazon, and Schwab.

Then, every ten to 15 minutes while the plane is airborne, the server uses radio signals to connect with an Inmarsat satellite overhead, and gathers incoming and outgoing e-mail messages and refreshed Web pages. Incoming messages are delivered to the passenger's laptop; outgoing messages are sent down to the land-based Internet for delivery anywhere in the world.

The data flow through Inmarsat at a pokey 2.4 Kbps, but thanks to heavy data compression, Yap says, browsing the cached Web pages and trading e-mail will be almost as transparent to the user in the air as on the ground. Woe to those who try to send or receive multimegabyte PowerPoint presentations, though; there will undoubtedly be a surcharge for large files, not to mention the wrath of other passengers when the network, er, crashes. Yap says higher-speed links will eventually enable passengers to shop online, pay bills, manage bank accounts, and even change travel reservations while up in the air using any Internet site, not just the ones that are preloaded onto the airplane's server. Just think: With access to Monster.com, you can surf for a new job from the comfort of the $4,000 roundtrip business-class seat your company just bought you.