This is not that unrealistic. Though it is a different airport and era, back in the mid 90's I used Delta from ATL - TPA. Seemed every Friday night when i wanted to get home to FL, the L-1011 we had assigned to us was needed elseswhere. Since TPA was such a short flight, I guess, and they could turn it around without impacting much, they shipped our plane off to another city while we waited for a replacement aircraft to come to the gate. They would point out that we were waiting for one from the international gates. But the plane was fighting traffic flow so we had to wait for the rush hour to be over. That always turned into a delay of several hours. This happened at least 6 times in 3 months.