Carrier route record
UAIAD→SAN
United Airlines · Washington to San Diego
- Flights
- 1,041
- Period
- September 2025 to August 2026
- Share of route
- 74%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on IAD to SAN earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 1,041 flights, with a median arrival 12 minutes early.
Set against the rest of the country, United's IAD to SAN record is 9 points better than the US average of 77.3%. That gap is worth roughly 88 fewer late arrivals for every thousand flights.
Key figures
On time
86.1%
Arrivals under 15 minutes late, of 1,028 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
0.67%
National rate is 1.89%
Whole route
82.9%
Every carrier on IAD to SAN, 1,402 flights
These figures cover 1,041 flights between September 2025 and August 2026. The median arrival is 12 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.
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Carrier by carrier
United against every carrier on IAD to SAN
United flew 1,041 of the 1,402 flights on IAD to SAN, most of the route. Its 86.1% on time is 3 points better than the route as a whole, which runs 82.9%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 86.1% to Alaska at 73.4%. 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) | 1,041 | 86.1% | 65 min | 0.67% | A+ |
| Alaska Airlinesthin sample | 361 | 73.4% | 48 min | 0.83% | C+ |
Flight by flight
United flight numbers on IAD to SAN
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
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 13 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am335 flights93.9%
- 11am–2pm364 flights84.0%
- 2pm–5pm—
- 5pm–8pm342 flights80.7%
- 8pm–5am—
Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 93.9% of the time, against 80.7% for the evening window. That is 13 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
August 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. July was the busiest month here, with 93 flights.
Across the week, Tuesday is the strongest day at 87.9% on time and Friday the weakest at 82.7%, a spread of 5 points.
Arrival by arrival
How late United on IAD to SAN runs when it is late
United on IAD to SAN often beats the schedule: 452 of 1,028 completed flights, 44%, arrived 15 minutes or more early. The 143 late arrivals split 61 under half an hour, 32 between 30 and 60 minutes, and 50 an hour or more.
- 15+ min early452 flights44.0%
- Within 15 min433 flights42.1%
- 15–29 min late61 flights5.9%
- 30–59 min late32 flights3.1%
- 1–2 hours late30 flights2.9%
- 2+ hours late20 flights1.9%
Scale runs 0% to 100%.
Share of 1,028 completed flights by arrival against schedule.
A late pushback is often recovered here: of 119 departures that left 15 minutes late or more, 38 still arrived on time. In the other direction, 62 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SAN.
The worst days
Worst days for United on IAD to SAN
The latest arrival of the period was on 7 August 2026, 7 hours 18 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across August, December, January and June, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 7 August 2026 | 7 hours 18 minutes | Carrier |
| 8 August 2026 | 6 hours 24 minutes | Late-arriving aircraft |
| 5 December 2025 | 6 hours 17 minutes | Late-arriving aircraft |
| 26 January 2026 | 5 hours 43 minutes | Extreme weather |
| 11 June 2026 | 5 hours 18 minutes | Carrier |
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 9,247 reported delay minutes.
- 38%National Airspace System
- 32%Carrier
- 19%Late-arriving aircraft
- 11%Extreme weather
38% 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 3,553 minutes out of 9,247, against a national NAS share of 21%. The split is drawn from 9,247 reported delay minutes.
Cancellations are rare at 0.67%, below the national 1.89% 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 4.9% land an hour or more behind schedule, against 8.3% 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 88.0% on time across 1,041 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. 1,041 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. 1,041 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 86.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,028 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 SAN73.4%
- 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 7.05 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.