WASHINGTON — The Federal Aviation Administration (FAA) has informed Boeing that several important documents provided as part of the agency's continuing certification process of the 737 MAX 7 jet are not complete, and that other materials require a reevaluation by the American aircraft manufacturer.

According to a letter obtained by the Wall Street Journal, the FAA is asking Boeing to reconsider some hazards categorized as catastrophic that do not involve human factors assumptions.

In its letter, the FAA states that the agency was unable to bring to conclusion some of Boeing's submissions due to missing and incomplete information regarding "human factors assumptions in catastrophic hazard conditions." The new letter raises apprehensions about the planemaker's calendar for commencing deliveries of the smallest variant of the 737 MAX family.

December 2022 is the deadline set by the FAA for 737 MAX 7 and 737 MAX 10 certification unless the manufacturer secures an extension from Congress. Boeing must meet new modern cockpit alerting standards that could remarkably push back the aircraft's delivery schedules.

The standards were mandated by Congress in late 2020 as part of the FAA's certification process after two deadly 737 MAX crashes that killed 346 people and caused the type to be grounded for nearly two years.

Boeing previously said it does not expect to obtain approval for the largest MAX 10 variant before next summer. In a new statement made by the company on Oct. 17, Boeing said it is committed to meeting all regulatory necessities to certify the MAX 7, and safety is paramount in this effort. The airframer also added that it would continue to prioritize being thorough and transparent in its documentation and interactions with the FAA.

Certifications of planes require extensive paperwork submissions and a detailed review of safety evaluations by the Federal Aviation Administration.

In the Sept. 19 letter to Boeing, the FAA expressed concerns that the planemaker would not be able to secure certification for the MAX 7 this year. Boeing must get the green light for the MAX 7 first, as the MAX 10 approval is dependent on some MAX 7 documentation.