CHICAGO (Reuters) - Boeing Co BA.N has canceled a conference call it had scheduled for Tuesday morning with airlines to discuss systems on the 737 MAX model that crashed in Indonesia last month, two sources familiar with the matter said.

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“Boeing has been - and continues to engage with our customers. We continue to schedule meetings to share information,” Boeing said in an e-mailed statement. It was not clear whether the call was being rescheduled.

A third person familiar with the matter said Tuesday’s conference call was one of a series of routine technical meetings that Boeing holds with airline operators in various regions of the world.

All 189 people on board a 737 MAX operated by Lion Air died when the jet crashed into the Java Sea on Oct. 29.

Shares of Boeing were down 1.5 percent in midday trading at $315.68, after opening significantly lower. The company’s stock has dropped 20 percent since it hit a 52-week high of $394.24 on Oct. 30.

The stock has fallen in a broadly lower market amid increasing scrutiny by regulators and pilots into cause of the first major accident involving the 737 MAX, the latest version of the U.S. aircraft manufacturer’s popular narrow-body plane.

Questions have arisen about the role that a new emergency system on the jet, designed to prevent the 737 MAX from stalling, may have played in the crash.

After the crash, the U.S. Federal Aviation Administration warned airlines that erroneous inputs from the anti-stall system’s sensors could lead the jet to automatically pitch its nose down even when autopilot is turned off, making it difficult for pilots to control the aircraft.

Boeing has already provided two updates for operators around the world that re-emphasize existing procedures to deal with situations relating to the system.

If a group conference call is rescheduled, a spokesman for the Allied Pilots Association, which represents American Airlines Group Inc AAL.O pilots, said his union would like to be included.

Previous calls regarding the 737 MAX have been between Boeing and airline management, with safety updates passed onto the pilots unions, sources have said.

A preliminary report on the Lion Air crash will be released on Nov. 28 or 29, according to Indonesian investigators who have analyzed the doomed jet’s flight data recorder.

Divers have yet to locate the airline’s cockpit voice recorder, which would shed light on pilot interactions, important for gaining a fuller picture of the circumstances of the crash.