WASHINGTON — The U.S. Air Force will delay a full-rate production milestone for the KC-46 aerial refueling tanker to the end of fiscal 2024 to correspond with a fix for one of the aircraft’s key systems, the service announced late Monday.

The Pentagon’s independent weapons tester — Director of Operational Test and Evaluation Robert Behler — intends to conclude operational testing of the KC-46 only after prime contractor Boeing fixes the tanker’s critical deficiencies and has finalized its production configuration.

“Accordingly, the Air Force will defer the KC-46 full rate production decision until after the completion of [initial operational test and evaluation], and the receipt of the statutorily-required Beyond Low Rate Initial Production report from [Behler],” the Air Force said in a statement.

The KC-46 program has several remaining category 1 deficiencies, the term used by the Pentagon to describe the most serious form of technical problems.

Two of the deficiencies involve the aircraft’s remote vision system, which is a series of cameras and sensors used by the boom operator to see outside the KC-46 and refuel other aircraft. The Air Force has contended that the RVS does not properly function in all weather and lighting conditions; the service has refused to deploy the KC-46 until the problem is fixed.

Boeing in April agreed to completely redesign the system on its own dime, which will take until at least 2023.

One other issue involves the KC-46 boom, which was developed to meet NATO-specific requirements but cannot refuel the A-10 aircraft. The Air Force is paying to redesign the boom actuator, as the service signed off on the original design and did not realize until afterward that it did not meet the specifications needed to refuel the A-10.

In March, the Air Force announced an additional category 1 deficiency after maintainers found fuel leaking between the tanker’s primary and secondary fuel protection barriers. It is unclear whether this is still a problem, as Boeing had already developed a fix and began retrofitting aircraft when the issue was revealed.

“Given its confidence in deficiency resolution timelines for both the aerial refueling boom and Remote Vision System, the Air Force is rescheduling the KC-46’s Full Rate Production Decision milestone to late Fiscal Year 2024,” the service stated.

The Air Force notes that delaying the full-rate production decision will not affect the program’s cost — which is locked into place courtesy of a firm, fixed-price deal with Boeing that holds the contractor financially responsible for cost overruns;nor will it cause the service to alter its current delivery schedule.

Boeing is already producing KC-46s at “full rate,” which for the program is 15 tankers per year. It delivered the first KC-46 to McConnell Air Force Base, Kansas, in January 2019. Since then, Altus Air Force Base, Oklahoma, and Pease Air National Guard Base, New Hampshire, have also taken on new KC-46s.

Boeing is set to produce 179 KC-46s over the program of record. The company has racked up cost overruns of about $4.6 billion in excess of the $4.9 billion contract it was awarded in 2011.