United Airlines extends Dreamliner grounding

MANCHESTER, ENGLAND - APRIL 24: Crowds gather to watch the new Boeing Dreamliner 787 arrive at Manchester Airport during it's tour of the world on April 24, 2012 in Manchester, England. The Boeing Dreamliner 787 is made of composite materials and uses 20% less fuel than equivalent aircraft. Thompson Holidays were the first Uk company to buy the new 787. (Photo by Christopher Furlong/Getty Images)
Christopher Furlong

WASHINGTON United Airlines (UAL) is keeping the grounded Boeing 787 off its schedule through June 5.

Investigators are still trying to figure out what caused a battery fire and another battery problem last month.

United spokeswoman Christen David says the plane could still fly earlier than that if a fix is found. At that point, it would be used as needed around United's system.

United says flights from Denver to Tokyo's Narita airport that were supposed to start on March 31 will be postponed at least until May 12. If the 787 isn't ready to go by May 12, United says it will begin the Denver-to-Tokyo flights once the 787 is ready.

The world's fleet of 50 787s has been grounded since Jan. 16

The news comes as Boeing is set to propose a plan to federal regulators to temporarily fix problems with the 787 Dreamliner's batteries that have kept the planes on the ground for more than a month, a congressional official told The Associated Press on Wednesday.

Boeing Commercial Airplanes CEO Ray Conner is expected to present the plan to Michael Huerta, head of the Federal Aviation Administration, in a meeting on Friday, the official said. The official spoke on condition of anonymity because he wasn't authorized to speak publicly. Boeing spokesman Marc Birtel said the company doesn't talk in advance about meetings with federal officials.

"Everyone is working to get to the answer as quickly as possible, and good progress is being made," Birtel said.