WASHINGTON - The National Transportation Safety Board is recommending to the Federal Aviation Administration that it require aircraft on trans-oceanic routes be equipped with devices that will allow searchers to find them if they crash.

The recommendations come more than 10 months after the still-unexplained disappearance of Malaysia Airlines Flight 370 with 239 passengers and crew on board while flying from Kuala Lumpur to Beijing.

The NTSB noted in a letter to FAA administrator Michael Huerta that searchers for the plane "have analysed and mapped more than 41,000 square kilometres of ocean floor" without finding the aircraft's cockpit voice recorder, flight data recorder or wreckage.

The NTSB is also responding to the nearly two-year search for the recorders from an Air France flight that crashed en route from Rio de Janeiro to Paris in 2009, killing all 228 people on board. The NTSB said it cost about $40 million to find the flight recorders in that case.

The NTSB recommended that planes be equipped with: a method of broadcasting to a ground station information to establish where a plane crashes within six nautical miles of the point of impact; a low-frequency underwater locating device that will function for at least 90 days; a crash-protected cockpit image recording system that would allow investigators to see actions taken by crew members.