Originally Posted by
cepheid
Actually, this appears to be changing on United. We just flew a pet in-cabin from overseas, and they collected the fare over the phone when we made the pet reservation. Possibly this is because it was an overseas flight, not sure... but they may ask for the payment when the reservation is made, rather than at the airport.
For domestic flight in-cabin pets fees are charged at the time the reservations are made. It is $125 one way. Totally refundable if you change your mind about taking your pet.