Sikorsky CH-53A Sea Stallion crash near North Sea off Oksbøl, Southern Denmark, Denmark

The Marine Corps CH-53A crashed into the North Sea off Denmark during the NATO exercise Northern Wedding, while returning to USS Guadalcanal. All five aboard were killed. The cause was given as a catastrophic tail gearbox failure traced to a manufacturing defect in a particular series of gearboxes; a new 50-hour magnaflux inspection of the tail gearbox mounts was subsequently introduced and much of the CH-53 fleet grounded until replacement gearboxes were available.