The four-engine bombers are due for upgrades to their cockpits, a process that will keep the jets stateside for an undetermined amount of time, Brown told reporters at the Pentagon via a video link from Al Udeid Air Base in Qatar. The B-1s have drawn praise for the amount of weapons they can carry, their accuracy in using those weapons and their reliability during the campaign against ISIS.

Brown was quoted by CNN as saying that other US and coalition aircraft would pick up the B-1s' missions during the upgrades.

"We actually have plenty of capacity with other platforms. We lose maybe a little flexibility. The B-1 is a workhorse. The fact that it can carry as many weapons as it can and stay airborne as long as it can, it does provide a great capability," he said.

Brown said the air campaign against ISIS will continue and the B-1s will likely be part of it again. "They will be back, I fully expect," he said. B-1s from the 28th Bomb Wing out of Ellsworth Air Force Base in South Dakota, home to 27 of the bombers, flew 490 sorties against ISIS in a six-month deployment that ended in January. They dropped 3,800 munitions on 3,700 targets. - NDTV