I was lucky enough to ride along on the proving flight with the GF BAC 1-11 to Bait-al-Falaj. It was a condition of the sale of the ex-Phillipines 400s (I think they were) that the CAA, who regulated Gulf at that time, would approve scheduled operations into Bait-al-Falaj. The aircraft was crewed by BAE pilots, but there were some GF ones there as well who had done the course.
It was an interesting day starting with the first approach and landing (down the valley going Northish, aim for the painted spot on the hillside, look right for the runway, turn just before hitting the hill and get it down quick on account of there's no option to go round, if I remember rightly. OK in a DC3, even F27, but challenging in the jet, they said).
Then a number of take-offs and landings with just the test crew on board, simulated engine failures at various stages, and then the same again with ballast up to MTOW (or some quite high number), and the aircraft passed with 'flying' colours.
The final departure, after a necessary change of the main wheels, had us all back on board, with some ballast and fuel for Bahrain, GF crew flying, and a failure at V1; Rex E was sitting beside me in the cabin and as we watched the crest getting closer he said conversationally "I've just done the course, I've been flying here for years, and what I know is we'll hit about 200ft below the top".
A few moments later, there was a shove in the back as the "failed" engine was recalled into service, and we lifted over the crest nicely.
The CAA gave their approval and the rest is history.