Warren Adelman's colleagues know him as "Thumbs": Like many executives, he is adept at checking e-mail on his BlackBerry and does it almost constantly.

Unable to do so during flights, Adelman welcomes business trips as "an opportunity to decompress a little bit from the constant flow of e-mail, perhaps catch up on a book."

"It's one of the few downtime environments you get in this day and age," said Adelman, president and chief operating officer of GoDaddy.com Inc., a registration company for Internet domain names.

An invasion of his sanctuary is imminent, though, as airlines around the world would make in-flight Internet services available.

JetBlue Airways Corp. began offering e-mail and instant messaging on one aircraft this month. Broader high-speed services, including Web surfing, are to come next year on some flights of AMR Corp.'s American Airlines, Virgin America Inc., and Alaska Air Group Inc.'s Alaska Airlines.

And in-flight entertainment provider Panasonic Avionics Corp., a unit of Matsushita Electric Industrial Co. Ltd., has been testing Internet offerings with Australia's Qantas Airways Ltd. Other airlines are to join next year.

Airlines see airborne Internet access, which typically uses Wi-Fi technology deemed safe for flights, as producing both revenue and a competitive edge against one another and over trains, buses and automobiles.

Frequent fliers said the temptation to go online would be overwhelming, though they were divided over whether they would rejoice.

Jay Pease, a regional marketing director for Exstream Software Inc., said he needed to rest during transatlantic flights for morning meetings in Europe. But he often has trouble sleeping, and he worried that "the temptation would be there to say 'I'll just log on and surf the Internet for a while.' "

Jon Carson, chief executive officer of online fund-raising company cMarket Inc., said that, between children, meetings and electronic interruptions on the ground, "I get some of my best work done on the plane."

Good decisions and breakthroughs often arise from "the kind of deeper, reflecting thinking" not possible when new messages continually arrive, Carson said.

Adelman's colleague, GoDaddy general counsel Christine Jones, disagreed.

"I would seriously turn cartwheels," said Jones, who admitted to responding to e-mail while sitting in church. "The carriers that don't offer it will start hearing from their customers, your frequent fliers: 'Hey guys, you have to get on board with it.' "

Peter Allen, chief marketing officer for the management consulting company TPI, said he already spent 80 percent of his flights using his laptop - often catching up on e-mail and waiting for an Internet connection upon landing to transmit those messages.

Robert Tas, chief executive of the online advertising company Active Athlete Media Inc., said he usually wound up reading printouts of articles, reports and other items he could read online. And, if he had Web access, he could dig deeper into items of interest.

"Reading time is still important," Tas said. "Having the Internet would allow me to do it more efficiently."

Frequent travelers said catching up with e-mail in the air freed up their time at their destination - in the hotel or back home with family.

"If I ended up feeling bad about it and resenting it, I would turn off my computer," said Andy Halliday, chief executive of the collaborative tribute site Tribbit.com. "It's still a choice. Right now, you don't have that choice."

Jim Lanzone, chief executive of IAC/InterActiveCorp's search company Ask.com, spent a recent 10-hour flight from San Francisco to London reading magazines and Steve Martin's

Born Standing Up

. He watched television shows on his iPod, and had DVDs of

The Wire

TV show ready for his return flight.

Lanzone said he did not mind that Internet access would cut into all that.

"If I had something on deadline, I'm not going to be able to relax anyway," he said. "I can enjoy DVDs, music and books more because I'll be able to get things off my mind."