Delta Air Lines was once again the best on-time carrier in the U.S. and Canada in September, according to data from aviation analytics company Cirium.

They were followed by Alaska, which consistently does well on this metric. Every major U.S. airline cancelled fewer than 1% of its flights for the month, though JetBlue was the least on-time carrier (just slightly worse than Frontier) and second-worst for cancelled flights (American was most-likely to cancel).

Overall, United and Spirit performed well. American, Frontier, and JetBlue perofrmed poorly. Wihle Southwest's on-time performance slipped to be worse than American's, they tied for U.S. industry-leading in completing and not cancelling their flights.

Given its scale, Delta's relative performance is even more impressive - and the distance American Airlines is behind becomes even clearer.

Operational performance isn't just on-time performance, of course. American generally ends up last for mishandled bags and lost wheelchairs, and also for involuntarily denying boarding to passengers due to oversold flights.

Among global airlines, Delta was third. The most on-time was Delta's vassal to the south, Aeromexico. Looking at performance over the past three months, Delta overcame a poor period to consistently hit high marks. They were tops in August also. July was brutal across-the-board, while August was a bit better and September pretty good for most carriers.

There's a relationship between most on-time airline and most on-time airport. Aeromexico was the most on-time airline, and Mexico City number two among airports. Delta was tops in the U.S. and Canada, and its Salt Lake City and Detroit hubs were both in the top 6 among the largest world airports for on-time performance. Honolulu, which often has the least weather to deal with, was in the number one slot.

Ultimately, September's airline punctuality rankings show that Delta is in the lead and United hasn't actually caught up - but also that American continues to slip. And JetBlue and Frontier, of course, can't seem to get their acts together. At least at Frontier 'paying with your time instead of money' is baked into the value proposition.

September's On-Time Rankings Are Out -- Delta Dominates While American Slips Further Behind