Unexplained aircraft accident is a nightmare for the airline industry. If you can not find the black boxes with all the flight data and the pilots' voices, it is almost impossible to determine the cause of the accident.

When the Air France plane AF-447 disappeared in the depths of the sea off Brazil in bad weather June 1, 2009 we searched frantically for the crash site to find the recording equipment and voice recordings.

But the area was too large to find the right before the distress signal from the black boxes died.

The automatic underwater transmitter ULB, Underwater Locator Beacon, it sends only signals for 30 days. Since the battery dies.

Why was the search for the plane and recording equipment to the long haul?

Only after two years and the fourth attempt succeeded in finding both the Cockpit Voice Recorder and the Digital Flight Data Recorder two weeks ago.

Now is a series of technical requirements in the airline industry from the international aviation organizations ICAO and EASA, reports the Danish newspaper engineer.

These include that the satellite constantly keep track of where an aircraft is, the direction in which it flies and what speed it has. But first on the wish list are better batteries in the black boxes so they can send distress signals for three months - signals strong enough to be perceived even if the plane would be at several thousand meters into the sea.