Confirmed reservation changed to standby

[Flash6305]

I have a confirmed reservation for my flight tomorrow, but when I tried to check in online, it says I have been put on the waitlist.  Phoned the SWA A-list reservation line, and they were no help at all.  Only suggestion was to get to the airport really early and see if an agent can help.    Has anyone ever had this happen?  I am a frequent flyer withSW, traveling 2-3times a month.  Never had this occur before

[dfwskier]

I've never had this type of thing happen on Southwest, but I have on American and Delta.

It could be that there's been an aircraft swap where a smaller  plane is being substituted for one with more seats -- thus causing this problem for multiple passengers.

Is there a different flight that would work for you?