Glasgow Airport to downtown Edinburgh

Paisley's Gilmour Street railway station is the nearest to the airport. Just one mile from the terminal, it can be reached by taxi or by regular bus services from bus stop bay 1 – located just outside the terminal building.

There are direct rail services from Paisley Gilmour Street to Glasgow Central, Ayr and Clyde Coast destinations.
Paisley Gilmour Street to Glasgow Central
Eight trains per hour (Monday-Saturday) and five per hour (Sunday).

Rail tickets from Glasgow Airport to Glasgow Central station, via Paisley Gilmour Street station, can be purchased from the SPT Travel Centre on the ground floor of the terminal building, adjacent to domestic arrivals.
When travelling to the airport from any station in Scotland, you simply ask for a rail ticket to Glasgow Airport and this is then valid on the train to Paisley Gilmour Street and the Arriva bus service from Paisley to the airport.

You can take a bus or train to Glasgow Central Station. FYI, there are two airports in Glasgow, so you should confirm which one you arrive in (I think Prestwick does the international flights...).

Then it's a short walk or bus ride to Glasgow Queen Street, which is where the trains to Edinburgh depart (there are a few trains per day to Edinburgh from Glasgow Central but they are VERY expensive and take MUCH longer).

It'll probably take a good three hours between the various trains to get from the airport to Edinburgh. If you are flying back out of Glasgow early in the morning, you should probably stay in a hotel near the airport as you must arrive 3 hours prior to a US bound flight. And I don't know if trains run at that hour.

Good call not to rent a car - the road situation in Edinburgh is a bit of mess now due to preparations to for the future tram system.

Kate