A couple of years ago on a trip from TUS-PHX-PVR on HP traveling with my wife, we left Tucson at 6:30am to Phoenix, changed to the plane to Puerto Vallarta. We departed on time and traveled south, passing over Tucson. A little later I noticed that we were turning left --- until the morning sun was shining through the right hand side window. I questioned our flight attendant (we were in F/C) if she knew what was happening--she told us that they had shut down one of the engines on our 737 due to overheating and that we had to make an emergency landing at the nearest airport, which was TUS. About 10 minutes later they made the announcement to the passengers in the plane. The landing did not seem out of the ordinary except for the emergency vehicles along the runway, and that they didn't use reverse thrust. we arrived back in Tucson about three hours after our origninal departure, and waited a couple of hours for a aircraft replacement. The worst thing was that they had to trash our F/C meals because they had been standing too long since our original departure!

I have been a frequent flyer for as long as there have been FF programs, and this is the closest thing to an in flight emergency situation I have experienced.