Pilots undergo recurrent checks and proficiency checks administered by check airmen that observe and evaluate to ensure compliance and standardization throughout the company and industry. These checks are pass or fail. Doctors, lawyers, and judges are not checked to ensure their ability to perform their duties.
For the event described by the NTSB to have happened, the wing flaps had to be extended at 39,000 feet. This takes hydraulic power which creates a substantial amount of noise from the hydraulic operating pumps. Most passengers have heard this when the flaps are extended during ground taxi. The noise is just as noticeable at high altitude.
During the ILS approach, the glide slope failed. The DC-10 ahead of us made a missed approach. I advised the first officer to change the decision altitude of 852 feet to the minimum descent altitude of 1,140 feet and that we would continue the approach to localizer approach minimums. I also stated that I started the timer at the outer marker.
I was confident of flying a successful single engine ILS approach. However, Murphy’s law was lurking. We were informed that the ILS at Keflavik was not available and was shut down for maintenance. We would have to do a non-precision VOR approach to an altitude well below the prescribed safe landing minimums. The autopilot was not approved for a single engine non-precision approach. I would manually fly the approach.