SEATTLE, Washington: A dispute with a sole supplier of a critical wing component has stalled production of Boeing's 777 freighter for nearly two months, while output of its 767 freighter and military tanker has also been disrupted, according to Boeing workers and court filings.

Boeing filed a complaint in August alleging that Florida-based supplier Vaero stopped delivering trailing-edge rib kits, halting work at the company's Everett, Washington, wing-production facility supporting the 777 freighter and 767 programs.

The disruption was costing Boeing as much as US$6.5 million a day, according to the complaint.

Boeing described the trailing-edge rib kit as an "indispensable" component and said Vaero was its sole supplier.

The companies reached a settlement in late September, but production of the 777 freighter has still not resumed, according to three Boeing workers familiar with the matter. They declined to be identified because they were not authorized to speak publicly.

The dispute has also disrupted production of the 767, which is produced as both a widebody freighter and the KC-46 aerial refueling tanker. Boeing has received some parts for the 767 line since the settlement, according to one worker.

The nearly two-month production disruption had not been reported previously.

Boeing declined to comment, while Vaero did not respond to requests for comment.

Boeing is now seeking to bring production of the trailing-edge rib kit in-house, according to two people familiar with the matter.

The component is used in wing assembly for the 767 and current-generation 777 freighter. Boeing's newer 777X is unaffected because it uses composite wings.

Without the Vaero components, Boeing removed two partially assembled 777 freighters from its final assembly line, according to one Boeing worker.

Reuters identified one of those aircraft as destined for FedEx, using data from aviation consultancy IBA. FedEx did not respond to a request for comment.

Boeing has delivered 21 777 freighters so far this year, company data showed. It also has several freighters whose wings were assembled before the supplier dispute and which could still be delivered before the end of the year, according to two Boeing workers.