The US Federal Aviation Administration has said that some undelivered Boeing 787 Dreamliners have a new manufacturing quality issue that the country's largest plane maker will fix before the planes are delivered.
The issue is "near the nose on certain 787 Dreamliners in the company's inventory of undelivered aircraft. This issue was discovered as part of the ongoing system-wide inspection of Boeing's 787 shimming processes required by the FAA", the aviation regulator said on Monday.
It said that "although the issue poses no immediate threat to flight safety, Boeing has committed to fix these aircraft before resuming deliveries".
The FAA also said it "will determine whether similar modifications should be made on 787s already in commercial service" after it conducts a review of data.
Boeing declined to comment. The company has about 100 undelivered 787s in stock.
The aircraft maker suspended deliveries of the 787 in late May after the FAA raised concerns about its proposed inspection method, saying it was "waiting for additional data from Boeing before determining whether the company's solution meets safety regulations".
The FAA in May had issued two airworthiness directives to address production issues for in-service aircraft.
Boeing's 737 Max and 787 jets have been afflicted by electrical problems and other issues since late last year. It had only resumed deliveries of the 787s in March after a five-month hiatus – only to halt them again in May.
Two US politicians said in May they were seeking records from Boeing and the FAA on production issues involving the 737 Max and 787 Dreamliner.
The FAA said in September it was investigating manufacturing flaws involving some 787 Dreamliners. Boeing said in August airlines operating its 787 removed eight jets from service as a result of two distinct manufacturing issues.
In September, Boeing said some 787 aircraft had shims that were not the proper size while others had areas that did not meet skin-flatness specifications.
Last month at a conference, the company's chief executive Dave Calhoun said the 787s were "performing beautifully".
However, he said "the FAA rightfully wants to know more about the analytics and process controls that we put in place, which are different than the ones that we had previously, so that we could be more perfect".
Mr Calhoun said he hoped the FAA's review of Boeing's approach was "measured in months and not longer than the calendar year".
In February, it was reported that Boeing was beginning painstaking repairs and forensic inspections to fix structural integrity flaws embedded deep inside at least 88 parked 787s.
The fuel-efficient 787 has been a hit with airlines, which have ordered about 1,900 of the advanced twin-aisle jet worth about $150 billion in total at list prices.
The FAA has been critical of some of Boeing's safety practices in recent years and imposed a $6.6 million fine on the plane maker in February for failing to comply with a 2015 safety agreement.
The agency did not allow the Boeing 737 Max to resume flights for about 20 months after two fatal crashes and called for significant safeguards to a key system.
The FAA told Boeing in May that its planned 777X was not yet ready for a significant certification step and issued a warning that it probably would not certify the aircraft until mid- to late 2023.