F9DEN→SFO

Frontier flew 604 of the 5,415 flights on DEN to SFO, about 11% of it. Its 67.2% on time is about level with the route as a whole at 65.8%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from United at 71.2% to Southwest at 52.6%.

The choice of carrier is not cosmetic here. United Airlines arrives on time 71.2% of the time; Southwest Airlines manages 52.6%. Sample sizes sit next to every figure, because a two-point gap across 1,438 flights means less than a ten-point one.

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.0% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

The 967 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 73.2% on time across 604 flights, 6 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 6 points of difference.

One caution: this is a thin sample. 604 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.