Route reliability record
SLC→SFO
Salt Lake City to San Francisco
- Flights
- 3,472
- Period
- July 2025 to June 2026
- Distance
- 599 mi
- Carriers
- 4
This route sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 3,472 flights, of which United Airlines flew 484 at 76.6% on time.
United Airlines is the most reliable of the three carriers covered here at 76.6% on time across 484 flights.
Key figures
On time
69.0%
Arrivals under 15 minutes late, of 3,434 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
0.95%
National rate is 1.81%
Best carrier
United
76.6% on time across 484 flights
These figures cover 3,472 flights between July 2025 and June 2026. Beyond the headline rate, 10.3% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on SLC to SFO
The choice of carrier is not cosmetic here. United Airlines arrives on time 76.6% of the time; Delta Air Lines manages 67.4%. Sample sizes sit next to every figure, because a two-point gap across 1,706 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 484 | 76.6% | 72 min | 0.21% | B+ |
| SkyWest Airlines | 1,104 | 68.8% | 76 min | 1.27% | C |
| Delta Air Lines | 1,706 | 67.4% | 52 min | 0.88% | C+ |
| Frontier Airlinesthin sample | 178 | 66.3% | 95 min | 1.69% | C |
United leads Delta by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am475 flights82.8%
- 8am–11am458 flights58.5%
- 11am–2pm666 flights71.2%
- 2pm–5pm863 flights72.5%
- 5pm–8pm157 flights75.5%
- 8pm–5am853 flights60.7%
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 82.8% of the time, against 58.5% for the morning window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 863 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 42 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
June is the worst month at 42.4% on time, 42 points below March, the best at 83.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. March was the busiest month here, with 325 flights.
Across the week, Tuesday is the strongest day at 76.6% on time and Monday the weakest at 62.7%. 14 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. National Airspace System accounts for 52% of the 68,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 52%National Airspace System
- 26%Carrier
- 21%Late-arriving aircraft
- 1%Extreme weather
52% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 35,000 minutes out of 68,000, against a national NAS share of 21%. The split is drawn from 68,145 reported delay minutes.
Cancellations sit at 0.95% against a national 1.81%, which is ordinary. Diversions add another 0.14%.
Connections and stage length
What a delay here actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.3% 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 599 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 77.2% on time across 3,471 flights, 8 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 8 points of difference.
The sample behind these figures is 3,472 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.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. March runs 83.9% on time and June 42.4%, a swing of 42 points. If the dates move at all, move them out of June before you think about anything else. 3,434 completed flights over 12 months sit behind that.
Common questions
SLC to SFO questions
How often is SLC to SFO delayed?
About one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 31.0% of the 3,472 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SLC to SFO?
United Airlines leads at 76.6% on time across 484 flights. Delta Air Lines is at the other end on 67.4%, a gap of 9 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on SLC to SFO?
The 5am–8am departure window is the strongest at 82.8% on time. The 8am–11am window is the weakest at 58.5%, 24 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are June delays on SLC to SFO?
June is the weakest month at 42.4% on time, compared with 83.9% in March. Across the year that is 42 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SFO to SLC — the return legseparate record
- Salt Lake City International (SLC) delay statistics
- San Francisco International (SFO) delay statistics
- United Airlines on-time record76.6%
- SkyWest Airlines on-time record68.8%
- Delta Air Lines on-time record67.4%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SLC to SFO and SFO to SLC are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.