Route reliability record
IAH→SAN
Houston to San Diego
- Flights
- 1,686
- Period
- September 2025 to August 2026
- Distance
- 1,303 mi
- Carriers
- 1
This route lands a B+, 4 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 1,686 IAH to SAN flights, with a median arrival 7 minutes early.
Best time to fly IAH to SAN: a 2pm–5pm departure, ideally on a Tuesday. Flights in that window arrived on time 84.6% of the time and Tuesday flights 89.7%, against 81.0% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
81.0%
Arrivals under 15 minutes late, of 1,678 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.18%
National rate is 1.89%
Best carrier
United
81.0% on time across 1,686 flights
These figures cover 1,686 flights between September 2025 and August 2026. The median arrival is 7 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 IAH 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 | 1,686 | 81.0% | 55 min | 0.18% | B+ |
Flight by flight
Flights on IAH 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 Houston 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. IAH → SANHouston to San Diego | United Airlines | 80.9% | 81.0% | 0.18% | 2pm–5pm, Tue | UA 2491 09:30 |
| 2. HOU → SANHouston to San Diego | Southwest Airlines | 73.4% | 73.9% | 0.71% | 8am–11am, Mon | — |
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 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 1,686 flights.
- 5am–8am—
- 8am–11am365 flights84.5%
- 11am–2pm197 flights77.2%
- 2pm–5pm456 flights84.6%
- 5pm–8pm305 flights78.4%
- 8pm–5am363 flights77.4%
Scale runs 70% to 90%. Rows with fewer than 30 flights show a dash.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 77.2% on time against 84.6% for 2pm–5pm. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 2pm–5pm window is the busiest, with 456 flights scheduled in it.
Explore
Filter IAH 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 IAH to SAN, the best departure window is 2pm–5pm at 84.6% on time and the worst is 11am–2pm at 77.2%, a real gap of 7.4 points. All US flights leaving 2pm–5pm ran 71.9%.
- 5–8am—
- 8–11am84.5%
- 11am–2pm77.2%
- 2–5pm84.6%
- 5–8pm78.4%
- 8pm–5am77.4%
best all US flightsScale 60% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 22 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 69.5% on time, 22 points below February, the best at 91.3%. 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. March was the busiest month here, with 152 flights.
Across the week, Tuesday is the strongest day at 89.7% on time and Thursday the weakest at 72.8%, a spread of 17 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 18,000 reported delay minutes.
- 34%Late-arriving aircraft
- 32%National Airspace System
- 29%Carrier
- 5%Extreme weather
32% 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 5,650 minutes out of 18,000, against a national NAS share of 21%. The split is drawn from 17,547 reported delay minutes.
Cancellations are rare at 0.18%, 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
5.2% 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.
The 1,303 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
The return leg runs 83.9% on time across 1,686 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,686 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. February runs 91.3% on time and August 69.5%, a swing of 22 points. If the dates move at all, move them out of August before you think about anything else. 1,678 completed flights over 12 months sit behind that.
Common questions
IAH to SAN questions
How often is IAH to SAN delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.0% of the 1,686 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is IAH to SAN compared with the rest of the country?
81.0% of flights arrive on time here against a national 77.3%, a difference of 4 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on IAH to SAN?
The 2pm–5pm departure window is the strongest at 84.6% on time. The 11am–2pm window is the weakest at 77.2%, 7 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 IAH to SAN?
August is the weakest month at 69.5% on time, compared with 91.3% in February. Across the year that is 22 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 IAH — the return legseparate record
- George Bush Intercontinental (IAH) delay statistics
- San Diego International (SAN) delay statistics
- IAH to ORD, a related route75.1%
- SFO to SAN, a related route62.2%
- IAH to DFW, a related route76.4%
- United Airlines on-time record81.0%
- Why the first flight of the morning is statistically safest
- Worst months to fly in the US, ranked by the data
Direction matters. IAH to SAN and SAN to IAH 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.