After a 10-day tour of Ireland next July, we are going go Belfast. After Belfast, we want to go to Scotland for a few days, and have actually already booked a flight back to the USA from Glasgow. What is the best way to get to Glasgow? Our options seem to be the following: Return to Dublin and fly to Glasgow, or take a ferry from Belfast and then a bus? (Flights from Belfast seem to be impractical.) I
Easyjet has direct flights from Belfast to Glasgow. Several flights per day for less than US$50.
easyJet from Belfast would also be my suggestion (I've done that in the past).
Though you can fly between the two locations, you can also take the ferry from Belfast to Cairnryan/Stranraer and from there the train to Glasgow. A ferry and train are not as quick as a plane, but they are more fun and less expensive.
Here is the Stenaline site to book ferry tickets: http://www.stenaline.co.uk/routes/cairnryan-belfast
Here is the train schedule from Stranraer to Glasgow: https://www.thetrainline.com/train-times/stranraer-to-glasgow-central
Thanks to all of you who have replied. I wasn't aware of EasyJet, because they don't yet have their July schedule, so their flights did not show up on any sites such as Kayak.