Yes. The vast majority of airlines DO NOT have a way for offline jumpseaters to list for the flight via phone number. Most of the time the ONLY option is to list at the gate. The only exceptions are FedEx, UPS, JetBlue, and AA. I have seen other posts here that list phone numbers for US Air, AirTran, etc. Just FYI, these are usually for listing yourself as a standby, which is incorrect and actually causes more headaches for the gate agent. If you are not absolutely positive that you being listed as a jumpseater via some phone number, it's better to do it at the gate.

Perhaps we can start a little list here? Does anybody else know who accepts listings via phone besides the four I listed above?