The numbers verify what I have seen anecdotally for some time: the WN ontime record is pretty weak. In the afternoons at LAS, I have often counted delays hitting one-fourth to one-half of the remaining flights, generally at least 50. However, it seems to have improved in recent weeks.
I have noticed the same delay patterns at other cities as well. I had one streak of eight itineraries in a row where something was late. The good news, of course, is being able to go standby on an earlier flight without paying the upcharge. But the bad news is I have enough spare time to tote up the number of late flights.
Predictably, the WN apologists have come out in force, with excuses such as other airlines padding their schedules. If they do, so what. Good service is largely delivering on what you promise. If you can't deliver, then don't make the promise and create realistic timetables.