It hardly matters. The air defense mission before 9/11 was carried out by 100% ANG forces, a split of part-timers and regulars. This is a side-effect of the downscaling of the armed forces over the last decade. Since the 50s it has been NORAD's mission, and the units that make up the force don't matter one way or another.
But for the record, Langley AFB is home to the 1st Fighter Wing, Air Combat Command; they fly F-15s. There's also a detachment of North Dakota ANG F-16s, and those were the ones who were scrambled 9/11.
/jordan