(Reuters) -RTX and the union representing around 3,000 striking U.S. Pratt & Whitney workers are resuming talks on Thursday as the stoppage continues in its third week, spokespeople for both the company and union said on Monday.

The International Association of Machinists and Aerospace Workers said the workers are on strike for improved job security and higher pay.

The first strike in more than 20 years at the enginemaker's Connecticut sites comes as the aerospace supply chain is already struggling to meet global demand for new airliners, while facing uncertainty over U.S. tariffs on imported aircraft parts. 

Pratt produces about 70% of the company's geared turbofan engine in Connecticut, where the strike is affecting two sites. The GTF is used in European planemaker Airbus' strong-selling A320 neo family, along with engines for the F-35 fighter jet.

Pratt has brought in engineers as part of its contingency plan to produce parts and avert delays, two sources told Reuters.

Pratt is sourcing engineers who can operate machinery as part of the plan, said one of the sources. A second source said he knows of engineers who have been reassigned to the plants, putting some engineering projects on hold.

Both of the sources discussed Pratt's internal labor strategy on condition of anonymity. RTX and the IAM declined comment on the use of engineers. 

A letter from Pratt to workers seen by Reuters asked employees to complete a skills assessment by last Friday. It called for workers with specialized manufacturing skills, along with general factory and business process support. 

"We rely on the talents of our entire workforce to meet our customer commitments," it said.

It's not clear that Pratt can keep all production moving or at what pace while using engineers in lieu of factory workers. An Airbus spokesperson said the company continues to monitor the situation and is in contact with RTX. 

Pratt and customers are still grappling with a manufacturing flaw discovered in 2023 that has grounded hundreds of aircraft while mechanics conduct months-long inspections. While some carriers like JetBlue have said they are seeing improvements with Pratt in recent months, roughly one-third of airplanes with GTF engines were out of service as of May 9, according to Barclays. 

Analysts warn that a lengthy strike would further strain production.