UASEA→SFO

United flew 2,040 of the 6,764 flights on SEA to SFO, about 30% of it. Its 66.5% on time is about level with the route as a whole at 65.6%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from Southwest at 100.0% to Alaska at 60.3%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 75.4% of the time; Alaska Airlines manages 60.3%. Sample sizes sit next to every figure, because a two-point gap across 2,716 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. 12.5% 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 679 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 75.8% on time across 2,042 flights, 9 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 9 points of difference.

The sample behind these figures is 2,040 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.