This was due to already serious existing issues, especially with the complex Remote Vision System that boom operators use to see what's going on at the back of the aircraft while linking up with receiving aircraft.
The Air Force announced that it had defined the KC-46A's fuel system leaks as a so-called "Category I" deficiency on Mar. 30, 2020. Category I issues are problems that would prevent the aircraft from performing one or more primary missions. The service also said that it had first become aware of the leaking in July 2019 during a test, but had initially categorized it as a less severe issue.
The refueling system aboard the KC-46 leaks fuel excessively. The problem has been known for eight months, but is now regarded as a third Category 1 deficiency. Here’s the USAF statement. pic.twitter.com/dQtYy7ZGel— Steve Trimble (@TheDEWLine) March 30, 2020
"The Air Force and Boeing are working together to determine the root cause and implement corrective actions," according to an Air Force statement. "The KC-46 Program Office continues to monitor the entire KC-46 fleet and is enhancing acceptance testing of the fuel system to identify potential leaks at the factory where they can be repaired prior to delivery." (end of excerpt)
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