SW seems to pull the plug quicker than most. In early March 2006 we had a 7 am AirTran flight out of PHL, we stayed at the Ramada the night before. Philly was due for an ice storm that morning. When we boarded the Ramada shuttle around 5 am it was drizzling, nothing much at all. The driver informed us to expect a madhouse in the airport because SW had already cancelled all flights. By the time our flight boarded it was still just a drizzle and we got away, no problems, as did another couple from Pa we met on these boards, on a later flight on AT. We won't use SW because of this.
Update: I just checked the AT flight we took back then, 620 at 7 am. It's half way to MCO right now, 8:45.
Bill From PA