When an airplane falls out of the sky, investigators need information from the plane's flight data recorders to pinpoint a cause in hopes of averting a similar disaster in the future. While airline crashes are extremely rare, accident analyses often yield information that leads to technical or operational changes that make air travel even safer.

The crash of Air France Flight 447 this week about 500 miles off the northeast coast of Brazil reportedly is pushing current crash investigation technology to the limits. And aviation experts already are warning that the plane's flight data recorder might never be found, given the depth of the ocean at the suspected impact area and the limitations of flight data recorders used in today's airliners.

The main problem facing searchers is that the electronic "pinger," attached to the flight data recorder, which sends out electronic signals to searchers, is likely resting on the ocean floor, some 20,000 feet below the surface, and the search area could be as large as several hundred square miles. Adding to these challenges is the fact that the ocean bottom in that area is mountainous.

Still, given today's electronic and communication technologies, failure to retrieve flight data from a commercial airline crash is not acceptable, even in water that is nearly four miles deep.

But there are solutions, well-known in the industry, that could prevent a repeat of the extreme challenges facing searchers in the Atlantic Ocean this week.

One possible solution, which has been installed on most military aircraft for 30 years, is a deployable flight incident recorder that detaches from the plane milliseconds before impact. Such deployable devices, already endorsed by the Federal Aviation Administration, would be located near the tail of the plane. The tail-mounted data recorder would be part of an inset, near the surface of the aircraft's skin, that would be ejected at the time of impact. By being separated from the plane, the recorder would avoid the worst level of impact and would be kept clear of intense fire, in the case of a land crash. In the case of a crash into water, the detached recorder would float, making it easier for searchers to use its satelite-compatible signal to locate the device and therefore to recover electronic evidence to help reconstruct the conditions that led to the crash.

Such modernization of flight data recorders to make them nearly 100 percent recoverable would ensure that no plane crash would remain a mystery, which is the possible fate of Monday's crash off the coast of Brazil that took the lives of 228 people.

Following the terrorist attacks of Sept. 11, 2001, in which the fight data recorders never were recovered, Congress began to press the FAA to move to flight data recorders that detach at impact. According to USA Today, the Transportation Security Administration plans this summer to test a recorder that deploys away from the aircraft on impact.

Another approach to flight data recording, made possible by advanced communication technologies, would have planes broadcast their flight data in real time to land-based recording devices. Still, some locater technology would have to remain on planes to guide search efforts in the event of a crash.

Many millions of dollars will be spent in the possibly futile effort to retrieve Flight 447's flight data recorder from the ocean floor. If deployable flight data recorders had been installed on the Airbus A330, there would be little doubt that the conditions that caused, or led to, the crash could be examined by crash investigators, and presumably changes could be made to avoid a repeat disaster.

The possibility of the data recorder on Flight 447 never being found because it rests on the ocean floor should provide motivation for requirements that airlines around the world adopt modern technology when it comes to deployable data recorders. Making air travel even safer in the future depends on it.