US air has a different caveat. You must book a certain level (more money) in coach in order to use miles to upgrade. An example I am looking at to Europe is PIT - Venice, then Barcelon-Pit. The lowest coach (not upgradeable) is $727. The lowest coach that is upgradeable with miles is $1170.00, Ny point, check with the airlines and find out their restrictions. Good luck.
Lynn