(1) Microsoft Flight Simulator at the time only offered Boeing airplanes in their product, it is not until MFS X that they decided to include the Airbus 320.

(2) The Boeing planes (767,757) were bigger than most airbus planes owned by American Airlines (UAL, AA) which are much smaller (319,320), the only airlines who at the time had a bigger airbus, was NW,and US air, (330), but why bother, when their was a handful of 767 and 757s comming from the east to the west with a full tank of gas.