New York (CNN Business) Pilots for Southwest Airlines (LUV) have sued Boeing for $115 million in lost compensation they say was caused by the grounding of its 737 MAX plane.

Boeing BA Southwest Airlines Pilots Association, in a complaint filed Monday on behalf of the pilots, claims"deliberately" misled pilots about the safety of the aircraft, which caused two fatal crashes in less than six months killing 346 people. It also alleges the grounding of the 737 MAX — which has resulted in thousands of flight cancellations at many airlines including Southwest — has reduced the pilots' opportunities for work. This has already resulted in lost compensation to pilots of more than $100 million, the complaint states, and the grounding is still ongoing.

The union says $115 million in damages will cover the wages pilots are set to lose by the end of the year, as well as 401(k) contributions, sick leave accrual and profit sharing.

"It is critical that Boeing takes whatever time is necessary to safely return the MAX to service," Jonathan Weaks, president of the union, said in the statement. "Our pilots should not be expected to take a significant and ever-expanding financial loss as a result of Boeing's negligence."

Boeing has already taken a huge financial hit from its troubles with the 737 MAX. In the most recent quarter , Boeing reported its largest loss ever — a $3.7 billion adjusted loss — as a result of the grounding. The company has also said it will set up a fund to distribute $100 million to the families of people who died in the crashes.

Read More