Reservation was made through American Express travel service as a one way ticket as I was not sure what our return date would be. At the airport We were not allowed to board the plane and not given our boarding passes until we bought a return ticket. If that is the policy why was that not stated at the time of reserving our ticket MEX - NY? It is much more expensive to purchase two one way tickets than to purchase a round trip. We were not told that a round trip ticket was required.