Delta have a big base at Amsterdam and maintenance ties with KLM. If the Squark showing an emergency was for technical rather than medical emergency, then Amsterdam would have super long runways, technical assistance and (possibly) a fresh crew. While maybe closer to Edinburgh/Glasgow on a map, when the time of descent is taken into account, Amsterdam was probably not that much longer away.

Much the same for Flybe, Manchester is a major centre for Flybe flights, although less of a base than it used to be. Again, if technical rather than medical, then Manchester could well have had an available spare aircraft, spare crew, available engineers/spares, or a flight onto which the diverted passengers could be put. The difference Windermere – Leeds and Windermere – Manchester is likely marginal.

If a captain has the luxury of time when declaring an emergency, then to me it makes sense to select an airport that is known to flight crew, that can offer maintenance assistance immediately, has plenty of ground staff back-up contracted to the Airline should passengers services be required, has stand-by crew available should the current flight-crew run out of hours etc. A ‘medical’ emergency is likely to lead to at least one and half hours delay on the ground, so available, airline dedicated ground staff will be called on to effect the turn-around and crew hours can become an issue. Most ground handling companies only employ enough staff to comfortably handle the anticipated traffic, diversions cause considerable problems and can knock-on to delays in processing the normal traffic. A ‘technical’ issue could well mean passengers disembarking, so ground staff essential for food vouchers/accommodation, transit lounge facilities, re-routing etc., while having type certified engineers and spares holding available ‘on the spot’ will cut the diversion time on the ground considerably.

While there are times when the crew have to get the aircraft onto the ground asap, more usually there is time to select which airport is likely to get them, or at least their passengers, back into the air and on the way to their intended destination with the least delay. I would think that thinking is shown in both of the examples quoted. Getting nearer to their destination is likely slower than turning back to get the assistance they need at an Airport that can provide it, rather than being stranded at an Airport that can’t (and that assistance is in many forms, often not related to the reason for diverting).

I am not in the industry, but like the postee a keen watcher from outside.