Why was my new bottle of soda flat when it was opened it?

I had a whole case of bottles that were flat - I found out that the caps still had a full quarter turn left before they were tight on the bottle. This particularly seems to be a problem with diet Mt. Dew in 24 oz. bottles. Try tightening the caps on every new bottle - and don't buy any bottles that don't feel tight and pressurized; if there is give when you squeeze it, then the carbonation has left the building.