The interesting thing here is that there is no category of visa provided for a foreign crewmember who deadheads offline on a domestic US segment (eg. BA pilot deadheads in on BA into SFO then deadheads on an AA flight from SFO-LAX to operate ex-LAX).

The US DHS has recently ruled that crewmembers in these categories may NOT enter on either C1D, D1, D2 or B1/B2 category visas as they receive remuneration for the offline deadhead segment which would then qualify as "illegal work". Hence they would need to have a temporary work permit such as an H1 to be allowed to perform this, but of course the occupation would not qualify for an H1 (not to mention that there wouldn't be enough time to go through the petitition process even if it did) so its kinda a catch-22.

This has caused a bit of a problem for airlines positioning crewmembers in irregular operation situations. Airlines are now forced to deadhead them on an international leg into the US (eg. BA would fly the pilot LHR-YVR and then offline deadhead from YVR-LAX to enter on a C1D in that case).