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General view of the Air Ethiopian Boeing 787 Dreamliner shows the rear roof of the plane burned, near the jet's tail. (Sang Tan/Associated Press)

U.K. air accident investigators are recommending that all Honeywell emergency transmitters should be temporarily disabled on Boeing 787s following a fire last week at London's Heathrow Airport.

The Air Accidents Investigation Branch also recommended that the FAA and other regulators carry out a safety review of lithium-battery powered emergency locator transmitter systems in other types of aircrafts.

In a report issued Thursday, the investigators said that the greatest damage to the parked Ethiopian Airlines Dreamliner occurred around the aircraft's Rescu406AFN emergency locator transmitter — or ELT — near the tail section of the plane.

Investigators said it was not clear if the fire was caused by the transmitter's lithium-manganese dioxide batteries or a short near or around the transmitter, but recommended that the Federal Aviation Administration switch off the Honeywell transmitter in all Boeing 787s "until appropriate airworthiness actions" can be carried out.

A spokeswoman for the investigation branch said the easiest way to make the transmitter systems "inert" — as set out in their recommendations — would be to take out their batteries.

Investigators acknowledged that the Honeywell ELT model is fitted in a wide range of planes and previously had experienced no similar issues.

"However, large transport aircraft do not typically carry the means of fire detection or suppression in the space above the cabin ceilings and had this event occurred in flight it could pose a significant safety concern and raise challenges for the cabin crew in tackling the resulting fire," the report said

Transmitter not obligatory in U.S. planes

Boeing spokesman Marc Birtel noted that the transmitter isn't required by U.S. federal aviation laws, but is required by some foreign regulators for their airlines or their airspace.

Birtel said the transmitter, which helps with search and rescue operations, takes about an hour to remove from a 787.

'We are confident the 787 is safe and we stand behind its overall integrity.'—Boeing statement

Spokespeople for Honeywell and the Federal Aviation Administration did not immediately respond to requests for comment.

When news of the Ethiopian Airlines' blaze at first broke last week, investors in Boeing were worried that the lithium ion battery problem that had grounded the whole 787 fleet in January for four months had not been fixed. However, the AAIB said early on there was no evidence that was the case in the Heathrow incident.

On Thursday, Boeing Co. said it supported the British investigators' recommendations — which it called "reasonable precautionary measures" — and was working with regulators to take appropriate action in response.

"We are confident the 787 is safe and we stand behind its overall integrity," the company added.

Shares in Boeing were up almost 2.5 per cent at $107.34 in morning trading on Wall Street.

Revolutionary jet

Boeing marketed the plane, which the company dubbed the Dreamliner, to airlines as a revolutionary jet which — thanks to its lightweight design — burns 20 per cent less fuel to comparable aircraft. Boeing, based in Chicago, has delivered 66 of the planes to customers with another 864 of them on order.

Half of its structure is made of plastics reinforced with carbon fibre, a composite material that is both lighter and stronger than aluminum. In another first, the plane relies on rechargeable lithium-ion batteries to start its auxiliary power unit, which provides power on the ground or if the main engines quit.

Problems with those batteries ultimately led to the grounding in January of the 50 Dreamliners flying at the time.

First, a battery ignited on a Japan Airlines 787 shortly after it landed at Boston's Logan International Airport on Jan. 7. Passengers had already left the plane, but it took firefighters 40 minutes to put out the blaze.

Problems also popped up on other planes. There were fuel and oil leaks, a cracked cockpit window and a computer glitch that erroneously indicated a brake problem.

United Airlines recently had several minor problems with oil leaks on the 787, forcing emergency landings. The maintenance issues, which often also happen on other jets, received extra scrutiny because of the 787's problems.

Then a 787 flown by Japan's All Nippon Airways made an emergency landing after pilots were alerted to battery problems and detected a burning smell. Both Japanese airlines grounded their Dreamliner fleets. The FAA, which just days earlier insisted that the plane was safe, did the same with U.S. planes on January 16.