SEATTLE, Jan 9 (Reuters) - The Federal Aviation

Administration has approved Boeing's ( BA ) largest variant of

its best-selling 737 MAX jet, the MAX 10, to move to the second

phase of flight testing on the plane's long-delayed

certification campaign, according to ‌a source familiar with the

program.

The company and FAA declined to comment.

Boeing ( BA ) executives have previously said they ​expect to finish

certification this year for the MAX 7 and 10, ‍the smallest and

largest variants of the popular single-aisle jet. ⁠The company

has more ⁠than 1,200 orders for the MAX 10 in its backlog,

according to aviation data analytics firm ‌Cirium.

Boeing ( BA ) has faced delays in ⁠the certification of ​its MAX 7

and MAX 10 ​models due to an engine deicing issue. The U.S.

​planemaker has also faced delays in certifying ⁠its widebody

777X jet. In October, the ‍FAA gave ​Boeing approval to raise 737

MAX production to 42 ‍planes per month, ending a ⁠38-plane cap

in place since January 2024.

The MAX 7 is a ‍shortened version of the two types already in

service, the MAX 8 and 9, which have accumulated tens of

thousands of flight hours.

Beginning deliveries of the MAX 10 is widely seen by

industry analysts as critical to increasing Boeing's ( BA ) revenue and

cash flow.

DEICING ISSUE UNRESOLVED

The FAA approval did not apply ​to ‍the MAX 7, according to

the source.

Phase two of the FAA flight testing involves the aircraft's

avionics, propulsion and other parts of the ​design, but the

deicing issue has not been resolved.

The MAX 10 competes with Airbus' A321neo and risks losing

more market share the longer it is delayed. This week, Alaska

Airlines ordered 105 MAX 10 airplanes and Alaska CEO Ben

Minicucci said he is confident the MAX 10 will be certified this

year.

"It's progress, but until (the MAX 10) ​is certified, it's

not," said Scott Hamilton, an aerospace analyst and principal

with the Leeham Company. Until there is a clear path to

certification, Boeing ( BA ) cannot start production at its Everett,

Washington, plant, he said.