Air Force releases reports on KC-46A Pegasus accidents, critical lessons learned

The U.S. Air Mobility Command (AMC) has released the findings of three detailed accident investigation boards (AIBs) concerning incidents involving its next-generation KC-46A Pegasus aerial refueling tankers. The reports shed light on the complex operational challenges and system limitations encountered during critical refueling missions, resulting in millions of dollars in damage, but fortunately, no fatalities or injuries.

“These investigations underscore the inherent complexities of integrating a new, sophisticated aircraft into a vital operational fleet and highlight the Air Force's proactive measures to enhance safety and effectiveness,” AMC said in a press release.

The incidents under scrutiny occurred on Oct. 15, 2022, and Nov. 7, 2022, involving KC-46A aircraft assigned to the 305th Air Mobility Wing at Joint Base McGuire-Dix-Lakehurst, N.J., and a more recent event on Aug. 21, 2024, involving an aircraft assigned to the 22nd Air Refueling Wing at McConnell Air Force Base, Kan.

Air Force Lt Gen Rebecca Sonkiss, AMC Deputy Commander, emphasized the strategic importance of the fleet and the Air Force's commitment to continuous improvement.

"The KC-46 tanker fleet will sustain our air refueling mission capabilities for decades to come," Sonkiss said. "Challenges with adding a new aircraft to the fleet are not uncommon, but we do not take these incidents lightly. We have used the lessons learned to refine our KC-46 operations, including focused training and guidance while partnering with the contractor to implement long-term solutions."

Early indicators and insights gleaned from these and other events have already prompted AMC to implement significant precautionary measures. These include specified training protocols for aerial refueling involving fighter aircraft and a crucial adjustment to the refueling envelope, increasing it from six feet to ten feet. This expanded envelope provides boom operators with additional time to react during critical situations and offers improved visual cues of receiver aircraft, mitigating risks associated with the KC-46A's unique boom characteristics.

October 15, 2022: Boom Strikes Tanker Tail Amid Nozzle Binding

The first incident detailed in the released reports occurred on Oct. 15, 2022, during routine air refueling operations off the U.S. East Coast. A KC-46A Pegasus, operated by the 2nd Air Refueling Squadron from Joint Base McGuire-Dix-Lakehurst, was attempting to refuel an F-15E Strike Eagle from the 335th Fighting Squadron, Seymour Johnson AFB, N.C.

During a breakaway maneuver, a nozzle binding accident took place, where the refueling nozzle became stuck within the F-15E's receptacle. This led to the air-refueling boom (ARB) striking the tail section of the KC-46A, causing substantial damage. While there were no fatalities, injuries, or damage to civilian property, the estimated damage to the KC-46A was significant, totaling $8.3 million.

The accident investigation board, led by Col Chad Cisewski, concluded that multiple factors substantially contributed to the mishap. A primary cause was identified as a limitation of the ARB control system itself. The boom operator inadvertently applied a radial force on the ARB, causing the nozzle to bind. This system limitation subsequently led the ARB into an uncontrollable upward motion, striking the tanker’s tail. Further, the AIB found that the F-15E pilot did not adequately consider KC-46A’s "stiff-boom" characteristics. The KC-46A's boom requires significantly more fore-aft thrust input from the receiver aircraft to move the boom telescope in and out while in contact, a characteristic that the F-15E pilot's actions did not fully account for, thus exacerbating the binding issue.

November 7, 2022: Damaged Nozzle During Training Exercise

Less than a month later, on Nov. 7, 2022, another KC-46A from the 305th Air Mobility Wing, operated by the 2nd Air Refueling Squadron, encountered a similar issue. The tanker had departed Naval Air Station Cecil Field, Fla., to refuel an F-22A Raptor from the 94th Fighter Squadron, Joint Base Langley-Eustis, Va., as part of a joint-force training exercise originating from Tyndall Air Force Base, Fla.

During the second air refueling attempt of the sortie, the KC-46A again experienced a nozzle binding event during a breakaway with the F-22A. While the boom did not strike the tanker in this instance, the bound forces exceeded the structural limitations of the ARB nozzle, causing it to be damaged beyond repair. The estimated damages for this incident were $103,295.12, with no fatalities, injuries, or collateral damage.

Col Justin Ballinger led this investigation board, which also determined that multiple factors were substantial contributors. The board highlighted the boom operator’s failure to verify that the ARB nozzle was completely clear of the F-22A’s air refueling receptacle before making further ARB control inputs. Manual control inputs by the boom operator created a radial force, causing the nozzle to bind within the F-22A’s receptacle. Like the previous incident, the F-22A pilot’s actions were also cited. The pilot did not adequately consider the KC-46A's stiff-boom characteristics, which resulted in a rapid forward movement of their aircraft relative to the KC-46A, contributing significantly to the binding and subsequent damage.

August 21, 2024: Critical Boom Failure Mid-Flight

The most recent incident covered by the released reports occurred on Aug. 21, 2024. A KC-46A Pegasus assigned to the 22nd Air Refueling Wing, operated by the 931st Air Refueling Wing, departed Travis Air Force Base, Calif., to refuel an F-15E assigned to the 366th Fighter Wing in support of Operation Noble Eagle, a critical homeland defense mission.

During the fourth air refueling attempt, the KC-46A again experienced nozzle binding in the F-15E receptacle. Upon release, the boom rapidly flew upward, striking the bottom aft portion of the KC-46A. The impact and subsequent violent oscillations of the boom—left and right—resulted in a critical failure of the boom shaft structure, with portions detaching from the KC-46A in flight. The KC-46A crew declared an in-flight emergency and safely returned to Travis AFB, where emergency response personnel met them.

The estimated damages from this severe incident were the highest of the three, at $14 million. Again, no fatalities, injuries, or damage to civilian property were reported. The accident investigation board, spearheaded by Col Diane Patton, concluded that the mishap was primarily caused by the boom operator's control inputs, coupled with the receiver aircraft’s excessive closure rate and instability, which collectively led to the boom striking the tanker aircraft with catastrophic results.

Moving Forward: Continuous Improvement and Contractor Partnership

The common threads in these incidents—nozzle binding, challenging boom characteristics, boom operator input, and receiver aircraft flight dynamics—paint a picture of the learning curve associated with a new air refueling platform. The Air Force's prompt response, including specialized training and expanding the refueling envelope, demonstrates a commitment to minimizing future occurrences.

"We are continually refining our tactics, techniques, and procedures," Sonkiss added, emphasizing the collaborative approach. "Our partnership with the contractor, Boeing, is crucial in addressing both immediate operational solutions and long-term system enhancements to ensure the KC-46A's reliability and safety."

While these three significant incidents have now been thoroughly investigated, the Air Mobility Command noted that another nozzle-binding incident occurred on July 8, 2025. The circumstances of this event remain under investigation, and upon its completion, AMC will determine if further mitigation efforts are required.