WASHINGTON (Reuters) - Southwest Airlines pilots predicted on Monday that the grounded Boeing 737 MAX airplane will return to the skies around February, weeks later than Boeing and airlines have projected.

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The Southwest Airlines Pilots Association (SWAPA), the union for the airline’s pilots, said it believes the aircraft, which was pulled from service in March after two fatal crashes, will likely resume flights in “probably a February time frame.”

Southwest, United Airlines and American Airlines currently estimate the planes will be available to fly in early January.

Boeing said Monday it is “working towards return to service in the fourth quarter.” A key step - a certification test flight by Boeing - is not expected until early November.

Last week, SWAPA sued Boeing alleging that the planemaker “deliberately misled” the airline and pilots about the 737 MAX aircraft. The grounding of the 737 MAX in March forced more than 30,000 Southwest Airlines flight cancellations, causing over $100 million in lost wages for pilots, the union said.

Boeing said last week it believes the lawsuit “is meritless and will vigorously defend against it.”

SWAPA said Monday the resumption of flights could be pushed beyond February.

The union noted that after the certification test flight, the European Joint Aviation Authorities Joint Operational Evaluation Board has to submit recommendations to the FAA’s Flight Standards Board.

“The timing here may be influenced by geopolitical disagreements and tensions; however, we are hearing some indications that those issues are being resolved,” the union said, adding that several other steps must follow including publication of an airworthiness directive and a 15-day public comment period.

Airlines will then submit proposed changes to the FAA Certificate Management Office and pilots must complete training.

Southwest is the largest operator of the MAX with 34 jetliners in its fleet when the aircraft was grounded worldwide following two crashes that together killed 346 people.

Southwest said Monday it was relying on information from Boeing and the FAA and “does not currently have a target date that we are working toward. We ... currently do not have MAX-related capacity in our schedule through Jan. 5, 2020.”

Boeing is under pressure to deliver updated software and training to regulators for the aircraft to fly again, and the company has been negotiating compensation with customers like Southwest over the financial hit from the grounding.

Southwest, with around 10,000 pilots represented by SWAPA, had 41 more MAX jets on order for this year alone.