Following the fatal crash of a Lion Air jet in Indonesia last week, Boeing has issued a warning to airlines operating its new 737 MAX about what to do in the event of an "angle-of-attack" sensor failure and avoid a risky nose-dive.
Neither carrier said they had received any reports from pilots of issues with the sensor, which calculates the "angle of attack", a measurement of the angle of the plane's wing and airflow needed to maintain lift.
The problem is centered around the 737 MAX's Angle of Attack sensor which may "tell" the pilots and the plane's computers that it's about to stall (aerodynamic) and put the 737 into a dive.
United said: "We are in receipt of a Flight Crew Operations Manual Bulletin, issued by Boeing, which applies to the 16 737 Max 8 aircraft now in our fleet".
"Any action that the FAA would take regarding that incident would have to wait until we have findings", agency acting Administrator Daniel Elwell said Monday after a speaking engagement in Washington.
Through September, Boeing has taken orders for 4,783 737 MAX aircraft with 219 delivered to customers.
Indonesia's transportation safety committee said it had agreed with Boeing on procedures that the airplane manufacturer should distribute globally on how flight crews can deal with the sensor problems.
An overview of the 737 MAX flight manual revision being issued by the FAA.
This warning extends to both Air Canada and WestJet pilots, since both the airlines use 737-Max planes regularly.
Indonesia's search and rescue agency on Wednesday extended the search effort for a second time, saying it will continue until Sunday.
Lion's earlier admission that the jet had a technical issue - and the captain's request to turn back to the airport minutes before the crash - have raised questions about whether it had faults specific to one of the world's newest and most advanced commercial passenger planes.
Meanwhile, the search operation to recover the passengers, crew and the airplane's cockpit voice recorder is ongoing.