Originally Posted by
Bonehead
I think that direct flights can involve aircraft changes. The certainly have in my experiences on other airlines.
When southwest books you on a direct flight (same flight number), they intend that you stay on the same plane. In fact, they actually expect that you DO NOT get off the plane at the stopping point at all - which I learned the sort-of-hard-way when I booked someone on a "direct" flight something like SAN-PHX-MDW-TPA... poor guy couldn't get off the plane for 12 hours. Oops. (This was a few years ago and I'm sure I got that exact routing wrong but it was SAN-florida 2 stops.) At least I learned the lesson without being in the seat myself!
This has its upside too though - I've booked people last-flight-of-day MSP-DEN-ONT on direct flights and when MSP-DEN got delayed while everyone else connecting in DEN got hosed, the DEN-ONT direct flight just went late.