Calhoun told CNBC he is confident "we will get an extension and that they will be certified as safe airplanes."

Boeing faces a late December deadline for the Federal Aviation Administration (FAA) to certify the MAX 7 and MAX 10 under existing rules. After that date, all planes must have modern cockpit alerting systems to be certified by the FAA, which would mean significant delays for the new MAX aircrafts' deployment unless Congress grants a waiver to extend the deadline.

Earlier this month, Republican Senator Roger Wicker unsuccessfully sought to attach an extension of the MAX deadline to September 2024 to a defense bill.

The requirements were adopted by Congress as part of certification reform passed after two fatal 737 MAX crashes killed 346 people and led to the bestselling plane's 20-month grounding.

Even with a waiver, it is uncertain when MAX planes could be approved. The FAA in an Oct. 12 letter said some key documents Boeing submitted in the agency's ongoing review of the MAX 7 are incomplete, while Boeing does not anticipate winning approval for the MAX 10 before next summer.

Boeing has won a string of orders for the two variants of the MAX as it makes the case for an extension. On Wednesday Alaska Airlines exercised options to order an additional 42 MAX 10 planes.

Last week, United Airlines Chief Executive Scott Kirby also backed the extension, saying it makes sense to have a common 737 alerting system. "It's a right safety outcome," Kirby told CNBC. "Changing the cockpit is a bad safety outcome."

United in 2017 ordered 100 MAX 10s. Without an extension United would convert some orders to MAX 8 and 9s, Kirby said, "and we're going to buy more Airbus 321 airplanes," which would impact Boeing's U.S. workers.

Calhoun said he did not "want to forecast dire outcomes but Scott's pretty right about what he sees."

Pilots are split, with the union representing Southwest Airlines pilots in support and the union representing American Airlines pilots opposed. Families of some MAX crash victims are also opposed.

(Reporting by David Shepardson; Editing by Mark Porter and Nick Zieminski)

By David Shepardson