Route reliability record
IAH→SJU
Houston to San Juan
- Flights
- 907
- Period
- September 2025 to August 2026
- Distance
- 2,007 mi
- Carriers
- 2
This route earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.3%. When something does go wrong the average delay runs about 50 minutes. That rests on 907 IAH to SJU flights, with a median arrival 9 minutes early.
Best time to fly IAH to SJU: a 2pm–5pm departure, ideally on a Tuesday. Flights in that window arrived on time 90.9% of the time and Tuesday flights 93.4%, against 84.8% for the route overall.
Set against the rest of the country, this route's record is 8 points better than the US average of 77.3%. That gap is worth roughly 75 fewer late arrivals for every thousand flights.
Key figures
On time
84.8%
Arrivals under 15 minutes late, of 902 completed flights
Avg delay
49 min
Across delayed arrivals only, not all flights
Cancelled
0.55%
National rate is 1.89%
Best carrier
United
85.9% on time across 864 flights
These figures cover 907 flights between September 2025 and August 2026. The median arrival is 9 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 SJU
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 | 864 | 85.9% | 43 min | 0.35% | A+ |
| Spirit Airlinesthin sample | 43 | 61.0% | 97 min | 4.65% | D− |
Flight by flight
Flights on IAH to SJU
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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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 10 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am381 flights80.5%
- 11am–2pm19 flights—
- 2pm–5pm364 flights90.9%
- 5pm–8pm8 flights—
- 8pm–5am135 flights85.8%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 2pm–5pm slot at 90.9% on time, ahead of 8am–11am at 80.5%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 8am–11am window is the busiest, with 381 flights scheduled in it.
Explore
Filter IAH to SJU 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 SJU, the best departure window is 2pm–5pm at 90.9% on time and the worst is 8am–11am at 80.5%, a wide gap of 10.4 points. All US flights leaving 2pm–5pm ran 71.9%.
- 5–8am—
- 8–11am80.5%
- 11am–2pm—
- 2–5pm90.9%
- 5–8pm—
- 8pm–5am85.8%
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 18 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.
April is the best month on the calendar at 93.3% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. July was the busiest month here, with 93 flights.
Across the week, Tuesday is the strongest day at 93.4% on time and Saturday the weakest at 77.0%, a spread of 16 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 6,773 reported delay minutes.
- 39%Carrier
- 30%National Airspace System
- 28%Late-arriving aircraft
- 3%Extreme weather
The largest share of delay minutes, 39%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,613 of the 6,773 delay minutes reported here. The split is drawn from 6,773 reported delay minutes.
Cancellations are rare at 0.55%, 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
Badly late arrivals are rare here: only 3.4% 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 2,007 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 88.7% on time across 909 flights, 4 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 4 points of difference.
One caution: this is a thin sample. 907 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.
Work out the risk of missing a connection in SJU after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 907 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 84.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 902 completed flights over 12 months sit behind that.
Common questions
IAH to SJU questions
How often is IAH to SJU delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 15.2% of the 907 flights in this analysis, against 22.7% nationally. Delayed flights are late by about 50 minutes on average.
How reliable is IAH to SJU compared with the rest of the country?
84.8% of flights arrive on time here against a national 77.3%, a difference of 8 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 SJU?
The 2pm–5pm departure window is the strongest at 90.9% on time. The 8am–11am window is the weakest at 80.5%, 10 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 November delays on IAH to SJU?
November is the weakest month at 75.0% on time, compared with 93.3% in April. Across the year that is 18 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
- SJU to IAH — the return legseparate record
- George Bush Intercontinental (IAH) delay statistics
- Luis Munoz Marin International (SJU) delay statistics
- IAH to ORD, a related route75.1%
- MCO to SJU, a related route73.8%
- IAH to DFW, a related route76.4%
- United Airlines on-time record85.9%
- Spirit Airlines on-time record61.0%
- 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. IAH to SJU and SJU 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.