NEW YORK, May 13 (Reuters) -

United Airlines may not take delivery of the Boeing

737 MAX 10 until 2027 or 2028 because of uncertainty

about when the plane will be approved for use, an executive for

the carrier said Tuesday.

Boeing ( BA ) has faced significant delays in getting the smaller

MAX 7 certified, which must happen before the U.S. Federal

Aviation Administration can then certify the larger MAX 10.

United Chief Commercial Officer Andrew Nocella told

reporters on the sidelines of an event that the airline is

taking MAX 9 airplanes as it waits for the certification of the

10.

"In supply chain terms, we want to make sure we get our

aircraft so we've committed to the MAX 9," Nocella said. "Until

we know the MAX 10 is going to be delivered, we don't want to

have an aircraft that doesn't arrive."

Nocella said United may not achieve its earlier goal of

being one of the first delivery customers for the MAX 10.

"We want to see the aircraft certified before we make

the firm commitment to convert our 9s to 10s."

Boeing ( BA ) did not immediately comment.

In 2017, United made a major order of the MAX 10, which is

larger and can carry more passengers. The 737 is Boeing's ( BA )

top-selling airliner. The FAA has currently capped production of

the MAX at 38 planes per month after a 2024 mid-air emergency.

The FAA must approve an engine de-icing fix for the MAX

7 before it can certify the

plane after Boeing ( BA ) in January 2024

withdrew a waiver request.

Alaska Airlines told Reuters last year it did

not expect to receive 737 MAX 10 airplanes until at least

mid-2026.

Nocella said there is no end in sight to supply chain

issues on engines and other parts.

The new 787-9 with updated interior "should have been

announced six months ago" but for supply chain problems, he

said, adding: "I don't have a crystal ball, I can't tell you

when it's going to be fixed."