Carrier route record

UASFO→STL

United Airlines · San Francisco to St. Louis

Flights: 204
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 SFO to STL lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 204 flights, with a median arrival 10 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate United on SFO to STL from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

80.7%

Arrivals under 15 minutes late, of 202 completed flights

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

0.49%

National rate is 1.81%

Whole route

65.8%

Every carrier on SFO to STL, 781 flights

These figures cover 204 flights between July 2025 and June 2026. The median arrival is 10 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

United against every carrier on SFO to STL

United flew 204 of the 781 flights on SFO to STL, about 26% of it. Its 80.7% on time is 15 points better than the route as a whole, which runs 65.8%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 80.7% to Southwest at 49.0%. 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.

On-time performance by carrier on SFO to STL
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines (this page)thin sample	204	80.7%	52 min	0.49%	B+
SkyWest Airlinesthin sample	235	77.6%	85 min	2.55%	B
Southwest Airlinesthin sample	342	49.0%	59 min	0.00%	F+

Departure window

When United runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 204 flights.

5am–8am—
8am–11am102 flights80.0%
11am–2pm81 flights87.7%
2pm–5pm—
5pm–8pm—
8pm–5am21 flights—

Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.

The best window here is not the first bank but the 11am–2pm slot at 87.7% on time, ahead of 8am–11am at 80.0%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 8am–11am window is the busiest, with 102 flights scheduled in it.

Across the year

United on SFO to STL through the year

Jul–Sep 2025107 flights78.3%
Oct–Dec 202553 flights84.6%
Jan–Mar 20263 flights—
Apr–Jun 202641 flights80.5%

Scale runs 70% to 90%. 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 80.7% on time across 204 flights.

Quarter by quarter United on SFO to STL held fairly steady: 78.3% in Jul–Sep 2025, 84.6% in Oct–Dec 2025 and 80.5% in Apr–Jun 2026. A spread of 6 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Delay causes

Why United runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 57% of the 2,024 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
57%
Carrier
32%
National Airspace System
11%

57% 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 2,024 reported delay minutes here, that single category outweighs weather by 57 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 2,024 reported delay minutes.

Cancellations are rare at 0.49%, 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

Badly late arrivals are rare here: only 4.5% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

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 63.6% on time across 207 flights, 17 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 17 points of difference.

One caution: this is a thin sample. 204 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 SFO to STL

Put together: treat all of this as provisional. 204 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 80.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 202 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures