French navy ships searching the Atlantic Ocean will dip a receiver into the water to pick up signals from the 4-inch "pinger" attached to the airplane's "black box" recorders possibly resting on the ocean floor.

The search will cost millions of dollars and involve sophisticated military equipment. It also could ignite a debate about whether airplanes should be equipped with recorders that float.

The Transportation Security Administration, prodded by lawmakers for years, plans this summer to test a recorder that detaches from an airplane in a crash, agency spokeswoman Kristin Lee said. House Democrats began urging a test shortly after the Sept. 11, 2001, attacks. The cockpit-voice and flight-data recorders never were found for the two planes that hit the World Trade Center.

"The circumstances of 9/11 have demanded the need for this type of recorder," former National Transportation Safety Board chairman Jim Hall said. "This (Flight 447) accident puts an exclamation point on it."

Spotlight on building better beacon devices

The detachable recorder emits a signal within minutes of a crash indicating its location, potentially saving days of searching and millions of dollars, said Hall, who consults for a New Jersey company, DRS Technologies, that makes the devices. Unlike standard black boxes that are embedded deep in an airplane's tail assembly, the detachable recorders would sit in an inset on a plane's tail, Hall said.

U.S. commercial ships recently have been required to install the detachable beacons to help rescue efforts if a ship sinks, said Francois Leroy, general manager of Teledyne Benthos, a Massachusetts company that makes pingers. Adding them to jets might be fruitless, though, because "an airplane hitting the water at great speed creates a violent impact" that could destroy the devices, Leroy said.

For now, searchers looking for the recorders from Flight 447 will undergo a painstaking process that began Tuesday when Brazilian military planes found a 3-mile swath of debris from the Air France plane in a remote stretch of the Atlantic Ocean.

Searchers will first do a complex study of wind and ocean currents to try to determine where the debris went Sunday, said Richard Limeburner, an oceanographer at the Woods Hole Oceanographic Institution in Massachusetts.

That could narrow the area where military ships will begin listening for the pinger. When ships pick up a signal, they will continue to move around the vicinity to find the loudest sound from the pinger, indicating the most likely spot where it's located, Leroy said.

At that point, unmanned, remote-controlled submersibles would be dropped in the water and lowered to the ocean floor to take camera or sonar images.

Workers on the ship can guide the submersibles and use their electronic arms to pick up objects that would be brought back to the ship, Leroy said.

Although the technology has been used for years, Leroy and others say Flight 447 will put it to an extreme test because the recorders are submerged under thousands of feet of water.

"I'm a little worried how deep" the recorders are, said Bill Voss, president of the non-profit Flight Safety Foundation. "We're closer to the limits of technology than I'd like to be."

Leroy said searchers "will be looking for a small object in the middle of an area that could be several hundred miles square."

Meanwhile, the Federal Aviation Administration plans to require by next March that black-box recorders meet stricter reliability requirements and hold more information critical to helping accident investigators solve crashes.

The proposal, first suggested by the safety board in 2005, would require cockpit voice recorders to be impervious to power failures and that the devices have two hours of recording time instead of the current 30-minute limit.

Hope of finding survivors dissolves

The chance of finding survivors in Flight 447 "is very, very small, even non-existent," said Jean-Louis Borloo, the French minister overseeing transportation.

The recorders may be the only hope in finding out what may have happened, Borloo said.

Borloo called the A330 "one of the most reliable planes in the world" and said lightning alone, even from a fierce tropical storm, probably couldn't have brought down the plane.

"There really had to be a succession of extraordinary events to be able to explain this situation," Borloo said on RTL radio Tuesday.

Contributing: The Associated Press