A ceremonial incomplete formation to honor a fallen teammate.
The missing man formation is a form of Due to the Dead performed by fighter jet pilots. It consists of a flight performing a flyby over a fellow pilot's funeral, either with one position conspicuously empty, or with one pilot sharply pulling away (straight up or sideways) just over the site while the others maintain course. Although primarily used in the military air force context, its variants can be used in other situations, as well. Compare Empty Chair Memorial and Riderless Horse. Since this is often a Death Trope, beware of spoilers.
Examples (salvaged from Due to the Dead):
Will go under Funeral Tropes.