I used to operate as a flight mechanic, this could be a charter aircraft, you would have a Maintenance REP (flight mech) on board with a portable personal tool box in a main deck closet and a FAK, fly away kit in one of the belly holds. This has contained in the past several sections of flexible hose, a 60 tonne jack, pipe swaging kits and sections of pipe. And a few belly cans full of every part (mostly electronic boxes) that if failed could ground an aircraft. This is done to allow a charter service to be anywhere at anytime w/o ground support. they are commonly used by sports teams, oil companies, cruise lines, casinos the big business right now is the military.