The fasteners, made from an aluminum alloy that makes them prone to cracking, were installed on wings, engine housings and parts of the fuselage in planes that entered Boeing's Seattle-area production lines since December, company spokesman Yvonne Leach said Tuesday.
Tuesday also marks the 27th day of a strike by about 17,000 Boeing workers, mostly in the Puget Sound area.
The AFL-CIO indicated Tuesday it plans to give financial support to the striking Boeing engineers and technicians.
The company determined that 20 aircraft currently in service may have defective fasteners, in addition to planes on the assembly line. The fasteners on all 20 planes, which are 737, 757 and 777 jets, have been tracked down and are all located in the planes' engine housings.
Boeing officials would not identify the airlines involved.
There have been no reports of fastener failures. Boeing met Monday with the Federal Aviation Administration, which determined that the problem will not pose a safety threat, Leach said.
"There would have to be at least four different things that would have to go wrong to even have a slight failure," Leach said.
On the production lines, all Boeing models are affected except the 100-seat 717 jetliner, produced in Long Beach, Calif., Leach said.
More than 330,000 of the fasteners were delivered to Boeing in November and December by a unit of Cordant Technologies Inc. of Salt Lake City. A cracking problem has occurred in "collars" used to help secure bolts to the aircraft.
Based on a preliminary assessment, Leach said, Boeing officials expect to be able to complete repairs and meet contractual commitments for delivery of the planes involved. She said the entire process of tracking down and removing the defective fasteners could take "a couple weeks."
Lauren Sides, a spokeswoman for Cordant, said the company received the wrong alloy from one of its suppliers. The difference in metals only became apparent through heat testing, she said. The company is working with its suppliers and its customers to track the defective parts.
Boeing announced Sunday that it would increase the pay of engineers and technicians, according to its last offer. But the offer didn't bring back any more strikers.
The union had no strike fund when the walkout began. It has received $140,000 in contributions. The King County Labor Agency says 225 strikers have received $68,000 for rent, utilities and child care. It expects to give $30,000 more by the end of the week.