Boeing reported mixed third-quarter results on Wednesday, as higher aircraft deliveries and a growing backlog of orders were offset by continued certification delays for its 777X jets.

CEO Kelly Ortberg said the first delivery of its next generation of long-haul, wide-body jets is now expected in 2027 instead of 2026, resulting in a $4.9 billion charge in the quarter through September. But Ortberg emphasized in a call with analysts that the delays stemmed from the certification process, and not from any newly discovered technical issues.

"While we are disappointed in the 777 delays, it shouldn't overshadow the progress we're making," he said.

Ortberg said Boeing was making progress on stabilizing its production. The aerospace giant delivered 160 planes in the third quarter, the most quarterly deliveries since 2018. The same time last year, Boeing said it delivered 116 planes.

Boeing also reported that its backlog of orders had grown to $636 billion in the third quarter. The growing backlog includes 5,900 commercial planes, with big 777X orders from Qatar Airways, which is waiting on 124 jets, and Dubai-based Emirates, which has ordered 205 of them.

"There's strong demand in our products," Ortberg said in an interview Wednesday morning with CNBC.

Boeing says the 777X "will be the world's largest and most efficient twin-engine jet," with a larger cabin and better fuel efficiency.

In September, the Federal Aviation Administration restored Boeing's ability to perform final safety checks and certify 737 Max jets for flight more than six years after two crashes of the then-new aircraft killed 346 people.

That decision was followed by the FAA's move this month to raise Boeing's 737 Max production limit that it had set in January 2024, after a door plug flew off an Alaska Airlines jet. Boeing is now allowed to build 42 Max jets per month, up from 38, and Ortberg said Wednesday that the company expects to raise that cap further once it demonstrates to the FAA that it can do so safely.

If the FAA approves future production boosts, Ortberg said, they'd come in increments of five jets and wouldn't happen more than once every six months.

"We won't move to higher rates until we reach stability and readiness," he said.

Boeing also reported $238 million in free cash flow, marking its first cash flow-positive quarter since 2023. But that figure was partly boosted by a delay in a potential $700 million payment to the Justice Department, part of a still-pending deal under consideration by a federal judge that could spare Boeing from criminal prosecution in the two deadly 737 Max crashes.

The crashes off the coast of Indonesia and in Ethiopia happened less than five months apart in 2018 and 2019 and were later blamed on a new software system that Boeing developed for the aircraft.

Meanwhile, a strike was ongoing at three Midwest plants in the St. Louis area. About 3,200 machinists who build military jets and weapons systems walked off the job on Aug. 4 as negotiations stalled over key issues, including retirement benefits and wage increases.

The workers rejected Boeing's latest contract offer over the weekend. It was the fourth time that the workers voted against a proposed deal.

"If Boeing is serious about culture change and rebuilding its brand, it starts with respecting the people who make its success possible," the union representing the workers said Wednesday in a statement after Boeing posted its quarterly results.

The strike is smaller in scale than a walkout last year by 33,000 workers who assemble commercial jetliners but still threatens to complicate the company's progress in regaining its financial footing.

Boeing said Wednesday it was still carrying out its "contingency plan" during the latest strike, which the company has said includes hiring replacement workers and leaning on its non-union workers during the work stoppage.

The company's stock price fell 4.7% in late-afternoon trading.