My major concern is not really directed at Southwest, but rather the FAA. The system they use to approve and monitor carriers allows the FAA's regional offices great leeway in how carriers are approved and monitored. The most immediate example is the way that Southwest is and was allowed to do their preflight announcements much differently then other airlines. No other airline, to my knowledge, was allowed to make that announcement humerous or anything other then a rote recitation of whatever was contained in that airline's flight attendant's manual.
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I am not sure of your experience, yet I assure you that PA's are changed all the time! They need to have the safety info at all times, but can be humerous at the same time. I recently nonreved and the "preflight" as well as others were sang with a unique Christmas theme. This was on Delta. I have heard numerous other "non standard" PA's on AA and CO. I have been a F/A for WN for 18 years and I travel on other airlines quite often.
Once again, If the info is in the PA, delivery can be unique!!!