I love Southwest cause I can call them up to 6 months AFTER a flight and provide the confirmation number, ticket number OR credit card and they send me the receipt by email or fax RIGHT AWAY (expense report reasons for me). Nobody does this except them. None of this - call this special number and by the way, you need the 50 digit ticket number to get this.

I think their service levels are far superior but that is a continually contested point. (Remember, I am a current AA Plat so I have been there, done that).