Help! Our flight out of Edinburgh has just been moved up a half an hour from 11:15 to 10:45. Not a big deal except that we will be leaving our tour group at the Glasgow Airport around 7:30. Any suggestions on the fastest way to get from Glasgow to Edinburgh airport on a Sunday morning?
I think you'll have to take a taxi or book a shuttle service, since buses and trains both require connections in the city center. See info at http://www.glasgowairport.com/im-arriving/onward-travel/. Is this a trans-Atlantic flight or within Europe (check-in requirements vary)?
Surely your tour operator will understand if you have to peel off early to make it to Edinburgh without it being a cliffhanger. Where will your tour group be earlier that morning? I second the advice to take a taxi or other direct shuttle; it would be worth it to have the peace of mind that they are dedicated to getting you there on time. I would advise aiming to get to Edinburgh airport no later than 8:15 to allow time for boarding pass check-in, security, passport control etc.
The saving grace is both airports are relatively small and not plagued by frequent traffic tieups like some of the big US airports.
The advice is to be at the airport 3 hours before a flight to the US, so unless you were planning on hiring a helicopter, you wouldn't hit this anyway!
A private transfer is your only option. Without any delays, this will take a good hour, so you are pushing it.