Hong Kong (CNN) -- The woes of Boeing's new 787 mount as U.S. regulators ordered airlines to stop flying their Boeing 787s. The U.S. move comes after two fleets of Boeing 787s have been grounded in Japan after alarms and a burning smell in the cabin forced a Dreamliner to make an emergency landing Wednesday. The incident is the most serious in a spate of problems that have bedeviled the new aircraft, and comes after the U.S. Federal Aviation Administration, which is responsible for air safety, launched a comprehensive examination on Friday of the Dreamliner's design as well as its manufacture and assembly.
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NEW: U.S. regulators Wednesday ordered airlines to stop flying their Boeing 787s
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Two fleets of Boeing 787s have been grounded in Japan after one jet made an emergency landing
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The woes come after the debut of the plane in 2011, nearly three years behind its production schedule
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About 50 aircraft have been delivered; Boeing has more than 800 unfilled orders from airlines
Related: More trouble for Boeing as @placeholder forced to make emergency landing