Well, the flight was headed to Detroit when it left London- it was not going to land in Scotland. Since it was buttoned up tight in flight- jurisdiction would be the territory of whatever country in which the aircraft was registered. It being a Pan-American airlines flight, that would be the US. There was also a deal made by the Scots with Libya to get two suspects extradited from Libya [which denied involvement], Scotland agreed to a trial in a third country, the Netherlands, on an old US base, so the Scottish court set up there at least for those suspects.
But, overall jurisdiction would be the registered country of the aircraft, if I recall correctly.
“Well, the flight was headed to Detroit when it left London”
No, the flight was heading to JFK first.