The Air Force’s multiple bands gathered last week for a rousing performance of “We Wish You a Merry Christmas” during their annual holiday “flash mob” — but it is likely to be the tradition’s finale.

In a release about the performance, which also included a choral rendition of the traditional song “Dona Nobis Pacem,” the Air Force Band said this is its fifth flash mob and the last one planned “at least for the foreseeable future.”

“We have had a good run of five years of these [flash mobs], and we are looking for new and innovative projects to move to next,” said Col. Larry Lang, Air Force Band commander and conductor, in a statement to Air Force Times.

The Nov. 29 performance at the Gaylord National Resort and Convention Center in National Harbor, Maryland, included members of all six performing flights of the Air Force Band, even veering through a section of dueling Irish fiddles from Celtic Aire and a swing interlude from Airmen of Note. Fourteen Irish step dancers and swing dancers ― who were not airmen ― joined the band for those sections. The band said that 150 Air Force musicians and 20 honor guard members took part in the performance.

The band’s release called the performance “the most complex and ambitious endeavor yet,” partly due to the large, cavernous venue and its challenging acoustics. Some members of the bands had wireless earpieces playing a pre-recorded version of the music with a “click track” metronome helping keep the beat and keep the bands in time.

Previous performances have included handbells, a World War II-themed swing performance in honor of the 70th anniversary of the war’s end, and a thunderous “Carol of the Bells” performed in the Air and Space Museum’s Udvar-Hazy Center. The band’s original flash mob in 2013 surprised visitors at the Air and Space Museum in Washington.