SEATTLE (Reuters) -Boeing CEO Kelly Ortberg said on Thursday that the planemaker is falling behind schedule on certifying the 777-9, its newest widebody jet.

The company expects to deliver the first 777X jet in 2026, six years later than anticipated when the program was launched in 2013.

A "mountain of work" remains to certify the plane, but no new technical problems have been identified, Ortberg said while speaking at the Morgan Stanley Laguna Conference.

But "even a minor schedule delay on the 777 program has a pretty big financial impact" for the company, which has already lost several billion dollars on the program, he noted.

Across its programs, Boeing's supply chain faces inflationary pressure, he said.

However, he does not expect any supply chain problems to prevent the company from increasing production of its best-selling 737 MAX to 42 aircraft per month by the end of the year, up from the currently federally imposed cap of 38, Ortberg said.

The company still has to stabilize one of its six key performance metrics before it increases 737 output, he noted.

Paying down debt is a top priority when the company returns to profitability, Ortberg said, noting that the company took on too much debt dealing with its crises in recent years.