I was on call for Y2k (fortunately at home in front of my computer) so I decided to take snapshots of who was flying during the Y2k event. The data comes from Flight Explorer.
For example, for the EST (GMT -5) Y2k transition, for flights that were mostly originating or departing in USA territory, American (AAL) takes the prize for fewer flights up at that hour relative to what they normally fly at that hour (only 8%).
Surprisingly to me, Southwest also had a relatively low rate at that time (18%).
Delta (DAL) was flying at 41%, the highest of the USA majors. This was followed closely by Northwest (38%), then United (31%) and Continental (29%).
What does this mean? Who knows! But the airlines will claim dimished business because of Y2k, and now I can guess who can make the biggest claims.