UPDATED with aircraft details AFA ORLANDO: After talking with the KC-46 commander and senior program officials, the head of Air Force acquisition has decided to halt acceptance of all Boeing’s troubled KC-46 tanker aircraft.

“As of this morning, we are still not accepting KC-46s and I believe this will continue for some time,” a somber Will Roper told reporters here this morning. “In this case it’s not clear how extensive the root causes are,” he told us. He said the Air Force will also inspect “planes we have already accepted.”

Government inspectors have found tools and other debris left behind on KC-46s at Boeing’s plant in Seattle.

UPDATED The Air Force has refused to take delivery of two tankers, which were awaiting formal acceptance. The Air Force had already accepted at least one aircraft and probably a handful more, but we don’t know the number.

Will Roper, head of Air Force acquisition

The Defense Contract Management Agency and the Air Force required Boeing to make 13 changes to procedures to ensure what’s called Foreign Object Debris will be effectively controlled in the future, Roper told reporters yesterday. But he was clearly troubled by what he heard when he spoke with the commander and the program office. Roper said he spoke with Gen. Maryanne Miller, commander of Air Mobility Command, twice already today. He said he would be visiting the Boeing plant soon but did not have date certain yet.

Boeing has faced a string of serious technical challenges, more than $3 billion in cost overruns and a year-and-half of schedule lapses building what was supposed to be a low-risk tanker derived from a commercial airplane.

But while tankers are not hig-tech, high-performance aircraft like stealth jets, they’re strategically essential to refuel the relatively short-ranged fighters so they can reach distant targets.The Air Force calculates it will need more tankers in the future, especially  in a major war because so many of the slow, bulky, vulnerable aircraft may be shot down.

Whatever happens with this, the American taxpayer will not pay a cent, because Boeing signed what’s called a fixed-price contract under which the government doesn’t have to help them cover cost overruns — a formula long advocated by the late Sen. John McCain. If fixing the problem costs Boeing anything, they will have to pay for it out of their own coffers.

Sydney Freedberg contributed to this story.