Equally as interesting as the IGS if not more so was the CC NDB ( twin NDB) approach in marginal weather. This was rarely in use and only if the IGS was down, usually awaiting flight calibration by the FAA Jetstar in those days.
I can still recall a United or maybe it was a Northwest 747 classic reporting at ELATO and ATC lady clearing the aircraft to CC for the twin NDB approach rwy 13.
"Say what?" in a Texas drawl, "ma'am I haven't done an NDB approach in 20 years, request clearance to Taipei" And off he went.