Originally Posted by
ElJudioErrante
If you omit to put FF nos in the reservation , then you can easily claim mileage per flight retroactively with the FF programmes of your choice.very simple
Depends on the OP's level with UA. If they are Premier Silver or above then they'll need their UA FF number in the reservation for access to Economy Plus seating at a minimum, but better zoned boarding is also pretty desirable on UA flights due to overhead bin shortages. If they have no status at all, then yes, do as you say and retroactively claim mileage later.