that is normal. the 13 year old is considered an unaccompanied minor therefore must be in the hands of the delta crew(airport and flight) from time you drop them off to the time you pick them up. of course you are to stay at the gate until the aircraft gets off the ground and the dad is suppose to be at the airport about 1 hr before arrival. before one could have gotten away from paying but with times the way they are, i'm sure they will be looking into that.