The Federal Aviation Administration (FAA) has asked Boeing Co B.A Re-evaluate its 737 MAX 7 safety file and say that some of the key documents submitted are incomplete and others require re-evaluation.

The move marks another setback for Boeing’s efforts to gain certification for the 737 MAX 7, a legal deadline of year-end.

According to a letter from the agency, the FAA cannot review the company’s filings “due to a lack of and incomplete information” regarding cockpit crews’ possible responses to catastrophic hazards viewed from the Wall Street Journal.

The FAA’s request for review concerns system safety assessments for the 737 MAX 7, the shortest of Boeing’s single-aisle jets, awaiting regulatory approval to carry passengers.

The agency recently said the plane was at risk of not being certified by one December deadline set by Congress after two fatal crashes involving the 737 MAX 8, an earlier version of the jet.

According to Boeing, safety remains the driving factor in its efforts to meet all regulatory requirements when certifying the 737 MAX 7. The company said that working thoroughly and transparently with the FAA will continue to be a priority.

Southwest Airlines Co LUV is a major buyer of the 737 MAX 7 and plans to add the fuel-efficient jet to its fleet and phase out older aircraft.

Boeing delivered 51 aircraft in June, exceeding the 50-aircraft threshold for the first time since March 2019.

Price promotion: BA shares are up 1.61% to $138.28 during the premarket session last check Tuesday.