Route reliability record
IAD→SAN
Washington to San Diego
- Flights
- 1,402
- Period
- September 2025 to August 2026
- Distance
- 2,253 mi
- Carriers
- 2
This route lands a B+, 6 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 1,402 IAD to SAN flights, with a median arrival 10 minutes early.
Best time to fly IAD to SAN: a 8am–11am departure, ideally on a Saturday. Flights in that window arrived on time 93.9% of the time and Saturday flights 86.7%, against 82.9% for the route overall.
Set against the rest of the country, this route's record is 6 points better than the US average of 77.3%. That gap is worth roughly 56 fewer late arrivals for every thousand flights.
Key figures
On time
82.9%
Arrivals under 15 minutes late, of 1,382 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
0.71%
National rate is 1.89%
Best carrier
United
86.1% on time across 1,041 flights
These figures cover 1,402 flights between September 2025 and August 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.
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Carrier by carrier
Which airline is most reliable on IAD to SAN
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 | 1,041 | 86.1% | 65 min | 0.67% | A+ |
| Alaska Airlinesthin sample | 361 | 73.4% | 48 min | 0.83% | C+ |
Flight by flight
Flights on IAD to SAN
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Washington to San Diego
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 1 of the top 2 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. IAD → SANWashington to San Diego | United Airlines | 85.5% | 86.1% | 0.67% | 8am–11am, Tue | UA 1930 09:00 |
| 2. BWI → SANBaltimore to San Diego | Southwest Airlines | 71.9% | 72.9% | 1.37% | 5am–8am, Sat | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 31 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am335 flights93.9%
- 11am–2pm364 flights84.0%
- 2pm–5pm—
- 5pm–8pm661 flights77.9%
- 8pm–5am42 flights62.5%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 62.5% on time, against 93.9% for the 8am–11am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5pm–8pm window is the busiest, with 661 flights scheduled in it.
Explore
Filter IAD to SAN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On IAD to SAN, the best departure window is 8am–11am at 93.9% on time and the worst is 8pm–5am at 62.5%, a wide gap of 31.4 points. All US flights leaving 8am–11am ran 83.9%.
- 5–8am—
- 8–11am93.9%
- 11am–2pm84.0%
- 2–5pm—
- 5–8pm77.9%
- 8pm–5am62.5%
best all US flightsScale 55% to 100%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 17 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
August is the worst month at 73.6% on time, 17 points below October, the best at 90.5%. 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 124 flights.
Across the week, Saturday is the strongest day at 86.7% on time and Friday the weakest at 79.3%, a spread of 7 points.
Delay causes
Why this route gets delayed
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 14,000 reported delay minutes.
- 42%National Airspace System
- 25%Carrier
- 24%Late-arriving aircraft
- 9%Extreme weather
- 0%Security
42% 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 5,782 minutes out of 14,000, against a national NAS share of 21%. The split is drawn from 13,789 reported delay minutes.
Cancellations are rare at 0.71%, 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 actually costs
5.0% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
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 is a different operation and performs like one: it runs 87.6% on time across 1,402 flights, 5 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 5 points of difference.
The sample behind these figures is 1,402 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in SAN after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. October runs 90.5% on time and August 73.6%, a swing of 17 points. If the dates move at all, move them out of August before you think about anything else. 1,382 completed flights over 12 months sit behind that.
Common questions
IAD to SAN questions
How often is IAD to SAN delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.1% of the 1,402 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is IAD to SAN compared with the rest of the country?
82.9% of flights arrive on time here against a national 77.3%, a difference of 6 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on IAD to SAN?
The 8am–11am departure window is the strongest at 93.9% on time. The 8pm–5am window is the weakest at 62.5%, 31 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are August delays on IAD to SAN?
August is the weakest month at 73.6% on time, compared with 90.5% in October. Across the year that is 17 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SAN to IAD — the return legseparate record
- Washington Dulles International (IAD) delay statistics
- San Diego International (SAN) delay statistics
- United Airlines on IAD to SAN86.1%
- Alaska Airlines on IAD to SAN73.4%
- IAD to ATL, a related route78.0%
- SFO to SAN, a related route62.2%
- IAD to DEN, a related route83.1%
- United Airlines on-time record86.1%
- Alaska Airlines on-time record73.4%
- 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
Direction matters. IAD to SAN and SAN to IAD are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.