United Airlines executives said they are encouraged by the more realistic timeframe for returning the Boeing 737 MAX to the skies

United Airlines will keep the Boeing 737 MAX out of service for even longer, and does not expect to fly the plane this summer, executives said Wednesday.

The additional delay follows Boeing's announcement Tuesday postponing until mid-2020 the target date for winning approval from regulators to return the MAX to the skies.

"We do not anticipate flying the MAX this summer," United Executive Vice President Andrew Nocella said on a conference call to discuss the airline's earnings.

United Chief Executive Oscar Munoz said the carrier remains confident the will ultimately return to service, dismissing a "worst-case" scenario where it is permanently removed from the lineup.

"We're actually encouraged at what we hope is a more realistic timeline and target," Munoz said, alluding to Boeing's goal dates that repeatedly lapsed in 2019.

The MAX has been grounded since mid-March following two crashes that killed 346 people.

On Tuesday, Boeing signaled the new "mid-2020" target to customers and suppliers, adding that "the FAA and other global regulators will determine when the 737 MAX returns to service."

There is expected to be a lag of at least a few weeks after regulators clear the MAX to fly, and when actually resume.

The statements from United came as the carrier reported a 39 percent jump in fourth-quarter profits to $641 million on 3.8 percent growth in revenues to $10.9 billion.

Executives confirmed that they are on track to add three more MAX simulators and they do not expect a potential requirement for pilot simulator training to further lengthen the MAX grounding.

But executives said delays in receiving new MAX planes hindered its growth plans in the United States. Like other leading carriers, United has little sense of how many new MAX planes it will add in 2020 and 2021.

"We're not where we'd like to be in Houston or Chicago," Nocella said. "We're behind schedule on where we'd otherwise like to be and we're likely to be behind schedule for the foreseeable future."

Shares of United fell 1.8 percent to $84.27.