Carrier route record
UAIAD→SAN
United Airlines · Washington to San Diego
- Flights
- 1,040
- Period
- July 2025 to June 2026
- Share of route
- 74%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on IAD to SAN earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 10 points better than the national rate of 77.6%. When something does go wrong the average delay runs about an hour. That rests on 1,040 flights, with a median arrival 11 minutes early.
Set against the rest of the country, United's IAD to SAN record is 10 points better than the US average of 77.6%. That gap is worth roughly 95 fewer late arrivals for every thousand flights.
Key figures
On time
87.1%
Arrivals under 15 minutes late, of 1,030 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
0.38%
National rate is 1.81%
Whole route
83.6%
Every carrier on IAD to SAN, 1,400 flights
These figures cover 1,040 flights between July 2025 and June 2026. The median arrival is 11 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 IAD to SAN
United flew 1,040 of the 1,400 flights on IAD to SAN, most of the route. Its 87.1% on time is 4 points better than the route as a whole, which runs 83.6%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 87.1% to Alaska at 73.5%. One 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) | 1,040 | 87.1% | 65 min | 0.38% | A+ |
| Alaska Airlinesthin sample | 360 | 73.5% | 48 min | 0.56% | C+ |
Flight by flight
United flight numbers on IAD to SAN
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–8am—
- 8am–11am334 flights93.3%
- 11am–2pm364 flights86.2%
- 2pm–5pm—
- 5pm–8pm342 flights82.0%
- 8pm–5am—
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 93.3% of the time, against 82.0% for the evening window. That is 11 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 364 flights scheduled in it.
Across the year
United on IAD to SAN through the year
July is the worst month at 76.1% on time, 19 points below September, the best at 95.4%. 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. August was the busiest month here, with 93 flights.
Across the week, Tuesday is the strongest day at 89.5% on time and Friday the weakest at 85.3%. 4 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
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 8,693 reported delay minutes.
- 31%National Airspace System
- 30%Carrier
- 27%Late-arriving aircraft
- 12%Extreme weather
Extreme weather accounts for 12% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 1.9 times the usual weather exposure. The split is drawn from 8,693 reported delay minutes.
Cancellations are rare at 0.38%, 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 4.7% 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 2,253 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 runs 89.5% on time across 1,040 flights, within 2 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. 1,040 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 IAD to SAN
Put together: treat all of this as provisional. 1,040 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 87.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,030 completed flights over 12 months sit behind that.
Related
Where to go next
- IAD to SAN, every carrier
- United on SAN to IAD, the return leg
- Alaska Airlines on IAD to SAN73.5%
- United Airlines network-wide record
- Washington Dulles International (IAD) delay statistics
- San Diego International (SAN) 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.