Carrier route record
UASTL→SFO
United Airlines · St. Louis to San Francisco
- Flights
- 207
- Period
- July 2025 to June 2026
- Share of route
- 26%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on STL to SFO draws a D+. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is a little over an hour behind schedule. Build slack into anything you connect to. That rests on 207 flights, with a median arrival 1 minute late.
The national on-time rate over the same period is 77.6%, so United on STL to SFO runs 14 points behind the country as a whole. Across a thousand flights that is about 140 extra late arrivals.
Key figures
On time
63.6%
Arrivals under 15 minutes late, of 206 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
0.48%
National rate is 1.81%
Whole route
63.0%
Every carrier on STL to SFO, 782 flights
These figures cover 207 flights between July 2025 and June 2026. Beyond the headline rate, 15.5% 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
United against every carrier on STL to SFO
United flew 207 of the 782 flights on STL to SFO, about 26% of it. Its 63.6% on time is about level with the route as a whole at 63.0%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 63.6% to Southwest at 62.5%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.
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 |
|---|---|---|---|---|---|
| United Airlines (this page)thin sample | 207 | 63.6% | 68 min | 0.48% | D+ |
| SkyWest Airlinesthin sample | 233 | 63.2% | 96 min | 2.15% | D |
| Southwest Airlinesthin sample | 342 | 62.5% | 58 min | 0.29% | D+ |
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 11 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–8am33 flights54.5%
- 8am–11am1 flights—
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm173 flights65.1%
- 8pm–5am—
Scale runs 45% to 70%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is the strongest at 65.1% on time. The full set of windows spans 11 points.
Across the year
United on STL to SFO through the year
- Jul–Sep 2025108 flights70.1%
- Oct–Dec 202553 flights79.2%
- Jan–Mar 20264 flights—
- Apr–Jun 202642 flights28.6%
Scale runs 20% to 85%. Rows with fewer than 30 flights show a dash.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 63.6% on time across 207 flights.
United on STL to SFO did not run the same all year. Its best quarter was Oct–Dec 2025 at 79.2% on time and its weakest Apr–Jun 2026 at 28.6%, a swing of 51 points on roughly 69 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
Across the week, Wednesday is the strongest day at 65.6% on time and Monday the weakest at 53.3%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. National Airspace System accounts for 43% of the 5,107 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.
- 43%National Airspace System
- 34%Late-arriving aircraft
- 19%Carrier
- 4%Extreme weather
43% 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 2,217 minutes out of 5,107, against a national NAS share of 21%. The split is drawn from 5,107 reported delay minutes.
Cancellations are rare at 0.48%, 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 costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 15.5% 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.
At 1,735 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 80.7% on time across 204 flights, 17 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 17 points of difference.
One caution: this is a thin sample. 207 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.
What to do with this
Booking United on STL to SFO
Put together: treat all of this as provisional. 207 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 63.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 206 completed flights over 12 months sit behind that.
Related
Where to go next
- STL to SFO, every carrier
- United on SFO to STL, the return leg
- SkyWest Airlines on STL to SFO63.2%
- Southwest Airlines on STL to SFO62.5%
- United Airlines network-wide record
- St. Louis Lambert International (STL) delay statistics
- San Francisco International (SFO) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.