I am somewhat familiar with weight and balance issues with aircrafts. I was curious though about some things I have experienced this morning and was hoping one of the experts may be able to share some insight. I am flying on USAirways flight 729 from LHR to PHL today and it is now delayed over 1 hour because of weight and balance issues. They actually called everyone seated in rows 16-32 and asked them to come to the desk so they could be reassigned seats outside this seat range. I have heard of the airline blocking off seats prior to online check-in when the loads are light which is the case on this flight (about 50% full) but never asking to reassign 16 rows worth of seats at check-in about 15 minutes prior to departure.

In addition, they now say we are waiting for aircraft maintenance to finish taping off the seats in rows 16-32 which I have never heard of before nor have I ever experienced even with flights on the A330-300 with similar loads. Does anyone have any ideas about why it would be necessary to actually tape off the seats and reassign so many seats at the last minute? The only thing I could think of for the last minute seat assignment changes is a change in cargo either less cargo or more cargo then expected, but I still don't get why they would tape the seats off. Does American not trust its passengers to follow the rules and thinks many passengers will move into these empty seats during the flight which will change the weight and balance of the plane?

I look forward to the insights. Thanks!