The Douglas DC-10
The DC-10 wasn't just a disappointment in the aviation world, it was a nightmare. There were a lot of oversights in terms of the construction which made it extremely dangerous. The last thing anyone wants to be is thousands of miles up in the sky trapped in a faulty plane.
The doors of the DC-10 were made to swing outwards, which made it extremely difficult to shut them correctly. In 1972, the doors swung open while the plane was in the sky. This happened again in 1974. In 1979, the wing had fallen off during takeoff. After some much-needed corrections, this plane is finally safe to fly.