A British Airways Boeing 747-400 comes apart piece by piece as a maintenance crew strips the aircraft down for a full overhaul. The film follows the engineers who inspect roughly twenty thousand individual parts, checking each one for wear, corrosion, or fatigue before the jumbo is cleared to fly passengers again. Cameras get into the sections travelers never see: the wing spars, the landing gear bays, the engine mounts, and the cockpit wiring, showing how a machine this size stays balanced and airworthy after years of hard use. The episode also tracks the other end of a 747's working life, showing what happens to an aircraft once it is retired from service rather than sent back into the air. Made as part of the Engineering Giants series on the world's largest machines, this installment treats the 747 less as a marvel to admire from a distance and more as a checklist of thousands of components that all have to hold.