The Federal Aviation Administration ordered the immediate temporary halt of U.S. Boeing Co.'s 787 Dreamliner flights on Wednesday, saying it requires a "corrective action plan" before flights can resume—and hasn't released a timetable for when that might happen.

The agency said it would work with Boeing and airlines to develop a plan to resume operations as quickly and safely as possible. United Continental Holdings Inc.'s United Airlines said it would immediately ground its six 787s under the FAA order.

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