The US Federal Aviation Authority (FAA) said on Thursday that it would permit Boeing to conduct test flights of its "Dreamliner" 787 airliners, to gather in-flight data on the planes' batteries and electrical systems.

#video#"As part of our ongoing efforts to determine the root cause of recent Boeing 787 lithium-ion battery incidents, the FAA will permit Boeing to conduct test flights of 787 aircraft to gather additional data," the US aviation regulator said.

The 50 Dreamliners in service were grounded worldwide on January 16 after unexplained overheating issues. A battery on one 787 melted mid-flight, while a battery caught fire on another Dreamliner after it had landed in Boston.

"The traveling public's safety is our highest priority," the FAA said in its statement. "These test flights will be an important part of our efforts to ensure the safety of passengers and return these aircraft to service."

Inconclusive findings

The FAA said the flights would only take place over unpopulated areas, and would be subject to more stringent safety rules than usual.

Initial safety reports have suggested that short-circuits within one of the battery's eight cells might have caused the overheating. An investigation by the National Transportation Safety Board, analyzing the Japan Airlines fire at Boston's Logan International Airport, said that a chain reaction known as "thermal runaway" spread through the other cells. Boeing contests this, however, saying that even when it tried to induce short-circuits, the problem would remain confined to a single cell.

The Boston plane was less than a month into its service life, having recorded only 169 flight hours at the time of the fire.

Boeing's 787 entered commercial service in October, 2011. The company is currently working on hundreds of outstanding orders for its new model.

msh/ch (AP, dpa, Reuters)