Join Date: Nov 2000
Location: Nashville -Past DL Plat, FO, WN-CP, various hotel programs
Programs: DL-MM, AA, SW w/companion,HiltonDiamond, Hyatt PLat, IHF Plat, Miles and Points Seeker
Posts: 11,405
As to what was a full flight suddenly showing lots of seats, I have seen that happen before. Between people that block seats (group) travel and code shares, there are situations where seats are not available.
Not sure if this is what happened to you.