Boeing says stabilizing 737 MAX production at 47 a month is taking longer than expected

Boeing chief executive Kelly Ortberg said at a Morgan Stanley conference on Wednesday that stabilizing 737 MAX production at 47 aircraft a month is taking longer than expected.

The manufacturer's shares fell 2.5 percent after the comments and closed the session down 4.5 percent.

Raising delivery rates on the single-aisle twinjet is central to the company's financial recovery, according to the account. Boeing carries net debt of close to 26 billion dollars and has taken what was described as a severe hit to its reputation after successive crises.

Ortberg also gave an update on certification of the 737 MAX variants. The largest version, the 737-10, will be certified very soon, he said, a process that has run several years behind schedule. The model accounts for roughly 30 percent of all orders in the 737 family, the source states. United States regulators certified the smaller 737-7 earlier this year.

The 787 Dreamliner program faces its own supply-chain setbacks. Plans to lift output of the widebody to 10 aircraft a month have been pushed back because of delays in engine supply. Boeing currently assembles eight 787s a month. Slow certification of premium cabin seats is also cited as a constraint in the account.