MELBOURNE, Australia — A U.S. Air Force Boeing KC-135R Stratotanker was damaged Tuesday during a ground-handling incident at an Australian airport.

A tug, under operation by Australian airlines Qantas, was pushing the KC-135R aircraft from its parking bay at Sydney’s Kingsford Smith International Airport when one of the tanker’s nose landing gear doors was damaged by the tug.

According to a source familiar with the incident, the incident fractured the KC-135R’s rear nose landing gear door; its planned mission is now canceled.

A second KC-135R, which had earlier been pushed back in preparation for takeoff, was also subsequently towed back by a replacement tug.

The two KC-135R tankers, call signs LULU23 and LULU24, are from the Air Force Reserve Command’s 72nd Air Refueling Squadron, 434th Air Refueling Wing, which is based at Grissom Air Reserve Base in Indiana and arrived in Sydney earlier in the week from Andersen Air Force Base in Guam.

Defense News understands their role was to provide tanker support for a pair of B-52 bombers, call sign ADIOS01 and ADIOS02, conducting an Air Force Global Strike Command training mission to Australia’s eastern seaboard the same day as the incident. The B-52s also arrived from Guam, where they were deployed on a rotational basis as part of Global Strike Command’s Continuous Bomber Presence mission.

While the damage to the KC-135R does not appear to be serious, its inability to take off to support the B-52s meant the bombers had to amend their initial plan to directly return to Guam after their training mission. The bombers instead diverted to Darwin in northern Australia to spend the night there.

Defense News has contacted both Qantas, who operated the aircraft tug involved in the incident, as well as Andersen Air Force Base for comment.