Route reliability record

SFO→SLC

San Francisco to Salt Lake City

Flights: 3,471
Period: July 2025 to June 2026
Distance: 599 mi
Carriers: 4

This route lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 3,471 flights, of which Delta Air Lines flew 1,708 at 78.1% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 78.1% on time across 1,708 flights.

On time

77.2%

Arrivals under 15 minutes late, of 3,440 completed flights

Avg delay

70 min

Across delayed arrivals only, not all flights

Cancelled

0.89%

National rate is 1.81%

Best carrier

Delta

78.1% on time across 1,708 flights

These figures cover 3,471 flights between July 2025 and June 2026. The median arrival is 6 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Which airline is most reliable on SFO to SLC

The three carriers here are closely matched: about a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on SFO to SLC
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,708	78.1%	77 min	0.88%	B+
SkyWest Airlines	1,103	77.2%	63 min	1.18%	B
United Airlines	482	76.7%	55 min	0.21%	B+
Frontier Airlinesthin sample	178	69.9%	82 min	1.12%	C

No carrier stands out. Delta tops the table at 78.1%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.

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 31 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am371 flights96.7%
8am–11am801 flights84.3%
11am–2pm673 flights68.7%
2pm–5pm491 flights66.5%
5pm–8pm1,019 flights76.5%
8pm–5am116 flights65.8%

Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 96.7% of the time, against 65.8% for the overnight window. That is 31 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 1,019 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 26 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.

Darker means more delays. Figures are on-time percentages.March best, June worst

June is the worst month at 61.8% on time, 26 points below March, the best at 88.2%. 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 324 flights.

Across the week, Saturday is the strongest day at 83.6% on time and Monday the weakest at 71.2%. 12 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. Late-arriving aircraft accounts for 52% of the 55,000 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.

Late-arriving aircraft
52%
Carrier
32%
National Airspace System
15%
Extreme weather
1%
Security
0%

52% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 55,000 reported delay minutes here, that single category outweighs weather by 38 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 54,603 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 96.7% on time here.

Cancellations are rare at 0.89%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here actually costs

7.7% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route are the a little over an hour kind, which a normal layover absorbs.

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 69.0% on time across 3,472 flights, 8 points below 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 3,471 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 88.2% on time and June 61.8%, a swing of 26 points. If the dates move at all, move them out of June before you think about anything else. 3,440 completed flights over 12 months sit behind that.

Common questions

SFO to SLC questions

How often is SFO to SLC delayed?

Roughly one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.8% of the 3,471 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on SFO to SLC?

Delta Air Lines leads at 78.1% on time across 1,708 flights. United Airlines is at the other end on 76.7%, a gap of about a point. 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 SFO to SLC?

The 5am–8am departure window is the strongest at 96.7% on time. The 8pm–5am window is the weakest at 65.8%, 31 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 SFO to SLC?

June is the weakest month at 61.8% on time, compared with 88.2% in March. Across the year that is 26 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. SFO to SLC and SLC to SFO 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.

Key figures