Be Really Careful with the I fares and read all of the restrictions... Several weeks ago my boss told me to book a trip from TPA to LHR for this week to be over there for 2 weeks. The R/T price was great for $2400 and I didn't even notice that it was an I fare. Early this week, I had to cancel the trip. The cancellation fee was $400, but get this... I could only use the remaining portion of a TPA - LHR... It has to be the exact same routing... No exceptions... I'll be doing London within the next year, so it's really not that big of a deal, but it's another case of buyer beware.