Qatar Airways said on Friday it had taken one of its Boeing 787 Dreamliners out of service following what it described as a "minor" technical issue, as pressure mounted on the plane maker over possible new electrical problems with the advanced jet.

The airline and Boeing declined to give further details but industry sources said they were treating seriously reports that the aircraft had been grounded for days after smoke was seen near an electrical panel.

The 787 has suffered a spate of mishaps in recent weeks, including a spontaneous fire on an Ethiopian Airlines-owned 787 that broke out while the plane was parked at a remote stand at London's Heathrow airport for eight hours on July 12.

According to Web-tracking service Flightaware, the Qatar Airways aircraft, registered as A7-BCB, has not flown since Sunday, an unusually long downtime for a long-haul jet designed to save on fuel bills.

Qatar Airways confirmed an aircraft had been taken out of service, but said no flights had been cancelled as a result.

"This is a minor issue for us, and not an incident, so we are not commenting," an airline spokeswoman said.

A spokeswoman for Boeing said, "We request that you channel all your enquiries to Qatar Airways."

Two people familiar with the matter, asking not to be identified, said smoke had been reported near an electrical compartment while the jet was on the ground in Doha. A failure in a similar bay caused a fire during a test flight in 2010, and three of the jets, including one owned by Qatar Airways, had electrical problems last December.

A fire-brigade supervisor in Doha said it did not have any record of an incident with an airport-related call last week.

India's aviation regulator said earlier it had started an investigation after an oven in a 787 operated by Air India overheated during a domestic flight, causing smoke.

There was no interruption to services.

Japan's ANA Holdings, which operates the world's biggest fleet of Dreamliners, also said on Friday it had found damage to the battery wiring on two 787 locator beacons, made by Honeywell International.

United Airlines said on Friday it also found a pinched wire in one of its locator beacons on one 787 in its fleet of six. It replaced the beacon and sent the defective unit to Honeywell for inspection. The work did not interrupt its schedule, it said.

The US Federal Aviation Administration and Boeing instructed airlines to inspect or remove the beacons, after UK investigators found two wires pinched together in the beacon inside the Ethiopian Airlines Dreamliner at Heathrow. The resulting fire caused extensive damage to the plane.

PAST PROBLEMS

Last December, three 787s had electrical problems that were made public. United Airlines experienced problems with electrical panels on two 787s, one of which diverted to another airport during a flight from Houston. Qatar Airways said that month that it grounded one of its 787 jets because of the same problem United had experienced. Boeing later traced the problem to faulty circuit boards in the panel.

In January, regulators grounded the global fleet of 50 Dreamliners after batteries burned on two jets within two weeks. Regulators lifted the grounding in April after Boeing redesigned the battery system, which supplies backup power to the jet and is unrelated to the emergency beacon, known as an emergency locator transmitter, or ELT, that is designed to send out a signal to help rescuers locate an aircraft wreckage.

Qatar Airways chief executive Akbar Al Baker said in May that the airline had to forego $200 million in lost profit because of the grounding of 787 planes, but has received compensation from Boeing for the losses. At least one other airline says it is still seeking compensation.

BOEING 'HIGHLY CONFIDENT'

Aviation experts say it is common for the reported number of incidents to rise when an aircraft is in the spotlight, and that all new aircraft models have incidents when they first enter service. The 787 began service in the fall of 2011.

Even aircraft with decades of service regularly suffer glitches that go unreported and rarely pose a direct threat to safety.

However, aviation experts say US and British authorities investigating the previous fires may seek to establish whether anything can be learned from a pattern of reported incidents connected in various ways to the jet's electrical systems.

Boeing chief executive Jim McNerney said this week he remained "highly confident" in the future of the 787 Dreamliner programme and the integrity of the company's newest airplane.

The 787 incorporates a raft of changes in the way passenger jets are designed, including greater use of electrical systems that save weight compared with older hydraulics. It is the first passenger jet built mainly from lightweight carbon-composites.

Boeing shares ended 1 per cent lower at $105.60 on the New York Stock Exchange on Friday. - Reuters