Boeing Co. (BA.N) met with 737 Max operators and lessors in Amsterdam on Tuesday, the first of about six sessions planned around the world as the planemaker lays the groundwork for resuming commercial flights of the aircraft following two deadly crashes.

Executives are using the sessions to discuss how to maintain the jetliners, which were grounded days after a March 10 disaster, said Boeing spokesman Gordon Johndroe. The meetings will also touch on plans to “turn the fleet back on” once regulators clear the Max to fly. Other topics include pilot training, software updates and a public campaign to bolster the jet’s bruised reputation.

“We know that we have a number of areas where we need to improve, including transparency,” Johndroe said in an interview.

Boeing is stepping up customer outreach two days after revealing it had known long before the first 737 Max crash in October that a cockpit alert wasn’t working the way buyers of the jet had been told. The manufacturer is finalizing an update for software that in both accidents pushed the plane’s nose down until pilots lost control. The changes will need to be certified by aviation regulators before the jet is cleared to resume commercial flights.

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“The decision to return the Max to commercial service rests in the hands of global regulators,” Johndroe said. “In anticipation of that day, we are meeting with our customers in regional conferences to talk through the activities to prepare the fleet and implement the software and training requirements.”

The U.S. Federal Aviation Administration has called for a summit of international regulators later this month to discuss its safety analysis of the aircraft. The European Aviation Safety Agency is running its own investigation into the design of the 737 Max and vowed not to allow flights of Boeing’s best-selling jet until the probe is finished.

The shares fell four per cent to US$356.83 at 3:19 p.m. ET after a downgrade by Barclays Plc, which said that investors were underestimating the fallout from the crashes. Boeing’s drop was the biggest on the Dow Jones Industrial Average, as U.S. markets fell sharply amid fears of a worsening trade war between the U.S. and China.