Pilots experienced these 6 problems with the Boeing 737 Max 8 in the months before its second deadly crash

In November, a pilot reported that a 737 Max 8's autopilot system made a brief, unwanted dip. The pilot said he or she resolved the issue after deactivating the autopilot system.

Another complaint from November mentioned a similar problem, as the aircraft dipped a few seconds after engaging the autopilot system. The captain immediately disengaged autopilot and returned the plane to its ascent.

The pilot expressed confusion about the incident.

"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.

In November, a pilot said a gap in the center pedestal of a 737 Max 8's cockpit allowed flight-related paperwork to fall from the cockpit onto the aircraft's wiring. Maintenance employees removed the papers from the wiring.

"Severe potential fire hazard!" the pilot wrote.

In November, a pilot criticized the 737 Max 8's flight manual for failing to include enough information about a system that automatically points the plane's nose downward if the plane senses it is flying at too steep an incline.

"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," the pilot wrote. "I am left to wonder: what else don't I know? The flight manual is inadequate and almost criminally insufficient. All airlines that operate the Max must insist that Boeing incorporate ALL systems in their manuals."

In October, a pilot reported that a 737 Max 8's auto-throttles, which regulate a plane's speed, didn't move into the correct position during the plane's ascent, though pilot noted that he or she may have made a mistake, rather than the aircraft.

"The FO (first officer) was still on his first month and was not able to identify whether it was the aircraft or me that was in error," the pilot wrote.

In September, a pilot reported that a 737 Max 8 burnt "significantly more fuel" than expected.

"My concern is that some MAX 8 aircraft are burning significantly more fuel than what is calculated on the Dispatch release. Perhaps the fuel bias on these aircraft needs to be re-evaluated," the pilot wrote.

The pilot wrote that a maintenance employee said a number of 737 Max 8's were not burning fuel efficiently. The maintenance employee attributed the phenomenon to Boeing's recommendation for engine-cleaning frequency, which the maintenance employee said was insufficient.