United has again captured the on-time arrival award for the month of September (88.9% of flights arrived on time), with US Airways (86.6%) and Continental (85.6%) close behind. Surprisingly, at least on first glance, Southwest Airlines finished last (75.8%) among major U.S. domestic airlines.
My first thought was dismiss the veracity of the data, concluding that United had just padded their flight schedules more than Southwest. But after comparing Untied and US Airways with Southwest on a multiple routes (two examples below), I was forced to reconsider.
Take a look at the following sample flights (n/s flights departing on the same day around the same time):