Interestingly, there is one place that no commercial flight that is not landing there is allowed to overfly, and that is the Tibetan Plateau. That is because it is so large in geographical extent that if a plane has an unplanned cabin depressurization situation over it, there is no way for it to reduce altitude following the regulation in a timely manner to the prescribed altitude, because that would place you underground. Only commercial flights landing at or taking off from Lhasa or another Tibetan airport is allowed to overfly the plateau, while transiting flights, no matter how many engines they have, are required to fly around it.
I have flown from Lhasa Gongar International Airport to Kathmandu across Mt. Everest, on a China Southern 757. It is kind of strange when they pressurize the plane after shutting the door to the standard 7,000' altitude, which is 4,000' lower than the altitude of the airport.
To bring it all back to 747, when was the first time you flew on a 747?
My first was in 1976. Air India Delhi Palam to Bombay Santa Cruz.
Second time was Sabena Brussels National Zaventem to New York JFK in September 1977.