For the whole picture: I am looking for an option to get from Oslo to Aberdeen in time to catch the 17:00 ferry to Kirkwall without having to spend a night somewhere on the way. I will likely not be able to be early enough at Oslo Airport to catch the 6:00 flight with a feasible transfer in Bergen, onward to Aberdeen.
Another option would be to fly to London Gatwick with a scheduled arrival 10:00 and continue with the 12:15 EasyJet flight to Aberdeen. I will have checked luggage. Is it realistic to have time for passport control (arriving on an international flight), pickup luggage, probably change terminals, check-in for the EasyJet flight, go through security and be in time at the gate with just 2 hours and 15 minutes between arrival and departure?
Edit: I didn't really mean this to be a question about other ways to get from Oslo to Aberdeen, but since people have started to suggest other alternatives, if anyone has an idea, that would of course also solve my problem. I am however planning to travel on December 29th and LoganAir does not have a direct route from Oslo to Aberdeen that day.
Other options I have considered:
Flying from Oslo to Aberdeen via Stavanger with arrival 15:25. Since the ferry check-in closes at 16:30, that does not seem feasible.
Flying from Oslo to Edinburgh and go by train to Aberdeen. There is a flight from Oslo arriving in Edinburgh 12:25, but since I would have to catch the 13:35 train from Edinburgh Haymarket to be in time in Aberdeen, that does also not seem feasible.
British Airways has a connection via London departing Oslo 07:00 and arriving in Aberdeen 12:40. Going by public transport, I am however not able to be at the airport before 6:17 and will not likely catch that flight.
The only other earlier flights from Oslo to Aberdeen are with KLM via Amsterdam and quite expensive.
The only earlier flight from Oslo to Edinburgh is via London with arrival 12:20, which is not much better than the direct flight arriving 12:25 and I would here also have to start with the 7:00 flight to London, which I will not likely be able to catch.
Flying all the way to Kirkwall instead of taking the ferry from Aberdeen. I wanted to avoid this option, since the LoganAir flights from the mainland to Kirkwall are very expensive.
Taking the ferry from Scrabster to Stromness instead of Aberdeen-Kirkwall, but I can also find no way to get to Scrabster in one day by 18:30 to catch the last ferry departing 19:00.