Southwest Airlines Boeing 737 MAX aircraft are parked on the tarmac after being grounded, at the Southern California Logistics Airport in Victorville, California on March 28, 2019.

PARIS — The pilots union for Southwest Airlines says it will ask Boeing for compensation to cover legal costs and lost income for pilots due to the 737 Max grounding.

The grounding in mid-March following two fatal crashes of the jet has run up legal fees for the Southwest Airline Pilots Association, which has had to comply with records requests as part of the Justice Department's investigation. Pilots have also lost wages over the last three months since the Federal Aviation Administration and other regulatory agencies said the Max cannot fly.

The pilots' union says it will be "seeking compensation and reimbursement from Boeing for every dollar legally available to be challenged, when the Max issues are resolved." The union hasn't said exactly how much the grounding of the Max has cost pilots. A person familiar with the matter estimates Southwest pilots lose $8.5 million per month not flying the Max.