Federal law enforcement agencies are seeking enhanced surveillance powers over Internet service on airplanes, an effort to shape an emerging technology to meet the government's concerns about terrorism.

Authorities want the ability to intercept, block or divert e-mail or other online communication to and from airplanes after obtaining a court order. Internet providers would have to allow government monitoring within 10 minutes of a court order being granted, be able to electronically identify users by their seat numbers and be required to collect and store records of the communications for 24 hours.

Such capabilities would go far beyond the government's current ability to monitor Internet traffic on land.

The FBI, Department of Justice and Department of Homeland Security jointly made the requests in a filing last week with the Federal Communications Commission, which is examining mostly technical changes to rules for satellite-based Internet services in hopes of spurring more deployment on airplanes. The service is available on some international airlines, but domestic carriers have not yet launched it.

The law enforcement agencies say they support giving travelers the ability to surf the Web and communicate via e-mail or instant messaging in the air but also fear that terrorists could use the services to coordinate an attack among themselves on a single plane, between aircraft or with people on the ground. The government also fears terrorists could use Internet-connected devices to detonate explosives via remote control.

"There is a short window of opportunity in which action can be taken to thwart a suicidal terrorist hijacking or remedy other crisis situations aboard an aircraft, and law enforcement needs to maximize its ability to respond to these potentially lethal situations," according to the filing, which was first reported by Wired News.

The petition comes at a time of ongoing controversy over how deeply security agencies should be able to penetrate private life in efforts to protect against terrorism.

"It does sort of make your head snap back," said James X. Dempsey, executive director of the Center for Democracy and Technology, a digital rights policy group. "Basically this is the full ability to control all communications into and out of" a particular spot.

Congress is wrestling with competing plans to renew the parts of the Patriot Act that expire at the end of the year. Civil liberties advocates say the law, which passed shortly after the 2001 attacks, is overly intrusive and want it scaled back, while law enforcement and the Bush administration want it renewed and in some ways expanded.

One proposal, passed by the Senate Intelligence Committee last month, would make it easier for the FBI to open mail and issue subpoenas without a judge's approval in terrorism probes. A House panel, meanwhile, voted to limit the FBI's ability to seize library and bookstore records during terrorism investigations.

For more than a year, the FCC has been separately considering whether companies that provide Internet access and carry Web traffic should be required to build surveillance capability into their networks.

Telecommunications carriers are required to do so under the 1994 Communications Assistance for Law Enforcement Act, and law enforcement agencies argue that the same standard should apply to any type of Internet communication, whether via cable lines, wireless, satellites or other technologies.

But the petition for in-flight rules goes well beyond the provisions in that 1994 law.

For example, Internet providers currently are not required to capture and store logs of Internet communications on their networks, which can carry hundreds of millions of e-mails per day.

Dempsey said the proposals -- such as the ability to disable the Internet use of some passengers while maintaining it for law enforcement or airline personnel on a plane -- amount to government-mandated design of the technology.

And if the proposals are approved, he said, he would expect law enforcement to argue that the same capabilities are needed on land.

A spokesman for the Justice Department said the agencies would not comment on the proposals pending congressional testimony scheduled for tomorrow by Deputy Assistant Attorney General Laura H. Parsky.

The business of providing Internet service on airplanes is just taking shape. Boeing Co. is the largest worldwide provider, but competitors are beginning to emerge, with Europe's Airbus SAS and Germany's Siemens AG announcing a partnership this week to create a similar service.

Boeing will abide by any government rules, company spokesman Terrance Scott said. But he added that the company questions whether the FCC's technical review of satellite services is the proper venue for examining surveillance rules, rather than Congress or the courts.

He said Boeing is still evaluating how much it would cost to comply with the proposed rules as well as the impact on the airlines and customers. Expense remains an issue for many U.S. carriers in deciding whether to offer the service, Scott said. The airlines split installation costs with Boeing and then share in revenues.

The Boeing Connexion service currently ranges in price from $9.95 for one hour to $29.95 for flights longer than six hours, Scott said. Customers sign on to and use the system in much the same way as commercial services provided at outdoor cafes, in airline terminals or other wireless "hot spots."

Much of the world is covered by satellites that transmit the signals, although some areas such as Australia and the South Pacific lag behind.

To date, Scott said, the service is not profitable.