LONDON, July 21 (Reuters) - The head of Boeing's ( BA ) defense

unit said Sunday the planemaker is still "fighting through

challenges" in building two delayed U.S. presidential aircraft

known as Air Force One.

In 2018, Boeing ( BA ) received a $3.9 billion contract to build

two 747-8 aircraft for use as Air Force One, to be delivered by

December 2024, but they are now delayed until at least 2027 and

2028.

Ted Colbert, who heads Boeing Defense, Space & Security,

said the planemaker is facing supply chain and other challenges

in building the airplanes.