For an explanation of part of the reason why Emirates chose GLA rather than EDI, see my post 1091 i.e.;
The PCNs and runway length are not too much of a problem for most long-haul aircraft types / likely routes provided that a suitable stand is created on the main apron e.g. by reinstating stand 6A. The A330 for example seems to be quite well suited to Edinburgh and even a 747-400ER has a useful payload/range from there.
The B777-300ER is least suited to the Edinburgh PCNs due to its very high ACN. Unless an ACN>PCN overload is sanctioned, Boeing's detailed performance figures indicate that MTOW from Edinburgh would be about 595,000lbs which would not be enough for Edinburgh - Dubai with a full passenger load, even with no cargo on-board, unless there was a substantial tailwind. As this is the mainstay of the Emirates fleet (the smaller Airbuses and Boeings are mostly due to be phased out) it's easy to see why Emirates has not yet chosen to operate from Edinburgh.
If a stand cannot be created on the main apron then the weak PCNs between the SE apron and Taxiway Alpha currently preclude regular long-haul widebody departures as the PCN is less than half the strength needed.
By way of comparison, here are the estimated maximum take off weights (MTOW) for a 773ER for GLA, NCL and EDI on a "Standard Day" assuming that ACN = PCN. (Sources of data are Boeing's detailed technical performance data for the 773ER and the NATS data for each airport).
Edinburgh;
MTOW = 595,000lbs. Limiting factor is the PCN of the main apron. At this weight it needs slightly less than 6,000ft of runway. The PCN of the runway is only marginally higher than the main apron so, if the aprons were strengthened it would make little difference to the calculation unless the runway and taxiway alpha were also strengthened. This assumes that a main apron stand can be created. The only place I think that might be suitable for a 773ER would be to create a diagonal stand where stands 11 and 14 are. The alternative would be to strengthen taxiway Lima and use the SE apron, although stand 17 is slightly too short for a 773ER. Perhaps that could be remedied by use of a pot of paint though.
Glasgow;
MTOW = 657,000lbs. Limiting factor is the PCN of the runway (NATS doesn't give PCNs for the aprons at GLA). At this weight it needs just over 7,000ft of runway.
Newcastle;
MTOW = 664,000lbs on runway 25 and 676,000lbs on runway 07. At these weights, the limiting factor is the runway length. The PCN of the main apron is good for 688,000lbs so a runway extension would increase the MTOW in the dry and an extension would be even more beneficial if the runway was wet. The runway PCN would be good for 728,000lbs if the aprons were stronger and the runway was extended by a few hundred metres. The advantage that Newcastle has is that its aprons and runway have a higher PCN that GLA or EDI even though its runway is shorter.
Just for a laugh, I checked to see what the MTOW would be at SYY.
Stornoway;
MTOW = 635,000lbs assuming that you park it on the runway, as the taxiways are too weak. Limiting factor for this is the PCN of the runway (not the length).
If a 10% ACN>PCN overload is allowed under CAP168 (this might happen or maybe it wouldn’t) then the above calculations would need to be revised.
Looking at these MTOW figures, it’s easy to see that Emirates B773ERs are much better suited to the PCNs at GLA and NCL than they are to the much weaker PCNs at EDI.
If, as has been rumoured, one of the other ME carriers is about to announce a route from EDI then it would require either a suitable stand to be created on the main apron or the links to the SE apron to be strengthened. As far as I know, all the stands on the main apron are too short and too narrow for an A330-200 (which seems to be the most likely equipment) so a diagonal stand would need to be created. Technically this is feasible but operationally it will present some challenges e.g. it will take up the space of two stands and stands are scarce at peak times. Also, who do you shift? BA? BMI? Someone else? Or use stands 2 and 3? Or ???
Even if a suitable stand could be created, given the multitude of factors that could delay either of the two aircraft occupying the stand before the A332 arrives and given the likelihood that the A332 will itself be delayed by a few hours from time to time, I can see many occasions when stand availability becomes an issue. It caused problems for Delta from time to time and, in theory at least, there were three stands on the main apron that were suitable for their B763 (2, 4 and 10, although BA seems to have virtually exclusive use of stand 10). In the short term there may only be one stand suitable for an A332 and that would require at least two ordinary stands to be simultaneously vacant.
As for Delta, their slot for the ATL flight at EDI was too late in the day (IIRC it departed EDI at 13:45) meaning that onward connection opportunities at Atlanta were less attractive. Every time I looked at connecting through Atlanta, my arrival time at my end destination in the USA was around midnight so by the time I would have collected my bags, picked up a hire car and driven to my hotel, then unpacked and got ready for bed it would have been 02:00 at best and probably a lot later. That may suit some people, but not me. Given the lack of large stands on the main apron at EDI, and the weak PCNs leading to the SE apron, I don't believe that an earlier slot would have been possible as there are only two suitable stands at the international end of the terminal and both of these were being used by a variety of B752s. If DL had been able to get a slot at EDI arriving at, say, 07:30 and departing at 09:30 I think their load factors and yield would have been a lot better. As it was, there were too many delays caused by the inadequacies of the infrastructure e.g. shortage of suitable stands and that ridiculous corridor arrangement which has been commented on previously in this thread.
I also considered taking the Delta JFK flight on a number of occasions. The problem with this flight was that the onward connections were terrible. Typically there was a 4 or 6 hour wait for a suitable connection and often this involved a change of airport to LaGuardia. CO connections via Newark were invariably far better.
The SFB and CAN flights this summer will presumably be operating from the SE apron because a B763W is too wide for stands 2 or 4. This will therefore involve a very significant ACN>PCN situation. This can be permitted on an occasional basis under CAP168 subject to very careful inspection of the pavement after each such operation but is unlikely to be permitted on a more regular basis, hence the reason why it is a very limited season of flights and the reason why long-haul ops with anything larger than a B752 are a rare occurrence at EDI.
For what it's worth, I don't think there will be any announcement of a ME route from EDI in the immediate future. If I were Ethiad, Qatar Airways or Gulf Air, I would see EDI's infrastructure as being less than ideal for the time being with the risk of resulting delays being too high. I hope I'm wrong but I suspect I am not. Time will tell.
For EDI to attract further long-haul it needs to invest in suitable facilities. It’ll be interesting to see whether the new owners will see this as a priority.