Boeing Chief Executive Dave Calhoun on Wednesday said "critics were right" to slam the planemaker' s 2018 $3.9 billion contract to build two new U.S. presidential airplanes.

Then President Donald Trump secured a promise from Calhoun's predecessor, Dennis Muilenburg, that the cost of replacing Air Force One would not exceed $4 billion.

"We didn't get enough price," Calhoun told CNBC.

Boeing previously took almost $1 billion in charges on the program and is up to three years behind schedule on the airplane.

The planemaker' s ailing defense business on Wednesday recorded a $2.8 billion charge for a number of programs, including Air Force One.