Carrier route record
UASFO→MIA
United Airlines · San Francisco to Miami
- Flights
- 623
- Period
- July 2025 to June 2026
- Share of route
- 36%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on SFO to MIA lands a B+, about a point 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 40 minutes on average. That is a workable record, not a spotless one. That rests on 623 flights, with a median arrival 1 minute early.
The US average over the same twelve months is 77.6%, so there is little to separate United on SFO to MIA from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.8%
Arrivals under 15 minutes late, of 620 completed flights
Avg delay
39 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.81%
Whole route
77.4%
Every carrier on SFO to MIA, 1,725 flights
These figures cover 623 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
Carrier by carrier
United against every carrier on SFO to MIA
United flew 623 of the 1,725 flights on SFO to MIA, about 36% of it. Its 76.8% on time is about level with the route as a whole at 77.4%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from American at 77.8% to United at 76.8%.
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 |
|---|---|---|---|---|---|
| American Airlines | 1,102 | 77.8% | 82 min | 0.91% | B+ |
| United Airlines (this page) | 623 | 76.8% | 39 min | 0.00% | B+ |
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 12 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–8am29 flights—
- 8am–11am310 flights69.7%
- 11am–2pm16 flights—
- 2pm–5pm—
- 5pm–8pm—
- 8pm–5am268 flights81.7%
Scale runs 60% to 85%. Rows with fewer than 30 flights show a dash.
The overnight block holds up unusually well at 81.7% on time across 268 flights. Red-eyes fly into empty airspace and empty gates, and they are the first rotation of the aircraft's day rather than the last. The 8am–11am window is the busiest, with 310 flights scheduled in it.
Across the year
United on SFO to MIA through the year
August is the worst month at 54.2% on time, 40 points below October, the best at 94.3%. 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. January was the busiest month here, with 62 flights.
Across the week, Thursday is the strongest day at 80.2% on time and Sunday the weakest at 73.9%. 6 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 52% of the 5,633 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%Late-arriving aircraft
- 22%Carrier
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 2,919 minutes out of 5,633, against a national NAS share of 21%. The split is drawn from 5,633 reported delay minutes.
Cancellations are rare at 0.00%, below the national 1.81% and low enough to earn the plus on the grade. Almost no flights are 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 3.4% 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 2,585 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 72.2% on time across 623 flights, 5 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 5 points of difference.
One caution: this is a thin sample. 623 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 MIA
Put together: treat all of this as provisional. 623 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 76.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 620 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to MIA, every carrier
- United on MIA to SFO, the return leg
- American Airlines on SFO to MIA77.8%
- United Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Miami International (MIA) delay statistics
- 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
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.