Several American pilots submitted complaints about the Boeing 737 Max aircraft months before the same model crashed in Ethiopia on Sunday, killing 157 people, NBC News reported.

The complaints, first reported by The Dallas Morning News, were revealed as the Federal Aviation Administration doubled down on its decision to let the Max 8 and Max 9 continue to fly in the United States.

At least five complaints about the Max 8 were made in October and November, and most mention issues with the aircraft’s autopilot and the plane going nose down shortly after takeoff. One pilot wrote that the Max 8’s aircraft manual was “criminally insufficient.”

“I think it is unconscionable that a manufacturer, the FAA, and the airlines would have pilots flying an airplane without adequately training, or even providing available resources and sufficient documentation to understand the highly complex systems that differentiate this aircraft from prior models,” one pilot wrote about the lack of instructions regarding the aircraft’s maneuvering characteristics augmentation system or MCAS.

The MCAS is a safety system installed in the Max 8 that would allow the aircraft to automatically correct itself if it enters a stall pattern, according to the Morning News. If the plane’s nose begins to point too far upward during takeoff, the system would take over and push the nose down, the Morning News reported.

“I am left to wonder: What else don’t I know? The Flight Manual is inadequate and almost criminally insufficient,” the pilot wrote.

In many of the complaints, the pilots noted the aircraft going nose down during takeoff.

One pilot wrote that “within two to three seconds the aircraft pitched nose down” after enabling the autopilot during takeoff. Once the autopilot was disengaged, the captain was able to continue climbing and the remainder of the flight was uneventful.

“We discussed the departure at length and I reviewed in my mind our automation setup and flight profile but can’t think of any reason the aircraft would pitch nose down so aggressively,” the pilot wrote.

Those complaints were logged after a Boeing 737 Max 8 crashed in Indonesia, killing 189 people.

The FAA declined comment to NBC News about the complaints.

Despite the crashes and complaints — in addition to calls from aviation experts and consumer advocates asking for the Max 8 to be grounded — major U.S. airlines are continuing to fly the Boeing 737 Max 8 amid the FAA’s insistence that the planes are safe.