The best price found from United States to Aran Islands is on September 1st, 2015, travelling with US Airways. See more options, compare prices and book: search flights.
All three islands have landing strips. The mainland departure point is Connemara regional airport at Minna, near Inverin (Indreabhán), about 35km west of Galway. Aer Arann Islands offers return flights to each of the islands several times daily (hourly in summer) for adult/child €45/25; the flights take about 10 minutes, and groups of four or more can get group rates.
If you work out some complex timings, you can visit more than one island in a day. A bus from outside Galway's Kinlay Hostel to the airport costs €3 each way.