Smaller planes that fly international routes may have turned from a domestic route. Also, operations often dictates gate assignments, unless the flight is an international arrival, where it has to arrive at an international gate connecting to FIS, unless the passengers have been pre-cleared.

I've seen some weird things happen in in the old DTW, where a DC-10 bound for Europe was departing from the D concourse, which was really crammed. Most wide-body flights bound for Europe and Asia back then departed from the F concourse.

Same goes for Continental in EWR.

- Pat