Route reliability record
STS→SAN
Santa Rosa to San Diego
- Flights
- 959
- Period
- July 2025 to June 2026
- Distance
- 508 mi
- Carriers
- 2
This route lands a B, 2 points worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 959 STS to SAN flights, with a median arrival 3 minutes early.
Best time to fly STS to SAN: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 90.6% of the time and Wednesday flights 88.9%, against 76.1% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.1%
Arrivals under 15 minutes late, of 933 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
2.50%
National rate is 1.81%
Best carrier
SkyWest
75.4% on time across 827 flights
These figures cover 959 flights between July 2025 and June 2026. The median arrival is 3 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 STS to SAN
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlinesthin sample | 132 | 80.3% | 64 min | 0.00% | B+ |
| SkyWest Airlines | 827 | 75.4% | 60 min | 2.90% | B |
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 30 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am362 flights90.6%
- 8am–11am60 flights80.0%
- 11am–2pm83 flights69.9%
- 2pm–5pm193 flights71.5%
- 5pm–8pm206 flights60.9%
- 8pm–5am55 flights62.3%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 60.9% on time, against 90.6% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5am–8am window is the busiest, with 362 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 22 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.
December is the weak month at 63.0% on time, against 85.2% in July. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. May was the busiest month here, with 125 flights.
Across the week, Wednesday is the strongest day at 88.9% on time and Friday the weakest at 68.2%. 21 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 13,000 reported delay minutes.
- 40%Late-arriving aircraft
- 30%Carrier
- 24%National Airspace System
- 6%Extreme weather
40% 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 13,000 reported delay minutes here, that single category outweighs weather by 7 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 13,431 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 90.6% on time here.
Cancellations run at 2.50%, against 1.81% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and stage length
What a delay here actually costs
7.1% 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 last about an hour, which a normal layover absorbs.
The 508 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 runs 78.8% on time across 960 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 959 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.
Work out the risk of missing a connection in SAN after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 959 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 76.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 933 completed flights over 12 months sit behind that.
Common questions
STS to SAN questions
How often is STS to SAN delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.9% of the 959 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is STS to SAN compared with the rest of the country?
76.1% of flights arrive on time here against a national 77.6%, a difference of 2 points against it. That is worth a B on this site's grading scale.
What time of day has the fewest delays on STS to SAN?
The 5am–8am departure window is the strongest at 90.6% on time. The 5pm–8pm window is the weakest at 60.9%, 30 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 December delays on STS to SAN?
December is the weakest month at 63.0% on time, compared with 85.2% in July. Across the year that is 22 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
- SAN to STS — the return legseparate record
- San Diego International (SAN) delay statistics
- Southwest Airlines on STS to SAN80.3%
- SkyWest Airlines on STS to SAN75.4%
- STS to SNA, a related route78.5%
- SFO to SAN, a related route66.6%
- DEN to SAN, a related route75.6%
- Southwest Airlines on-time record80.3%
- SkyWest Airlines on-time record75.4%
- The US routes with the most cancellations
- Why the first flight of the morning is statistically safest
Direction matters. STS to SAN and SAN to STS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.