Route reliability record
SJU→IAH
San Juan to Houston
- Flights
- 909
- Period
- September 2025 to August 2026
- Distance
- 2,007 mi
- Carriers
- 2
This route 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 11 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 909 SJU to IAH flights, with a median arrival 16 minutes early.
Best time to fly SJU to IAH: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 96.1% of the time and Wednesday flights 92.2%, against 88.7% for the route overall.
Set against the rest of the country, this route's record is 11 points better than the US average of 77.3%. That gap is worth roughly 114 fewer late arrivals for every thousand flights.
Key figures
On time
88.7%
Arrivals under 15 minutes late, of 903 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.55%
National rate is 1.89%
Best carrier
United
89.5% on time across 864 flights
These figures cover 909 flights between September 2025 and August 2026. The median arrival is 16 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 SJU to IAH
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 | 89.5% | 52 min | 0.46% | A+ |
| Spirit Airlinesthin sample | 45 | 72.7% | 83 min | 2.22% | C |
Flight by flight
Flights on SJU to IAH
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 16 points, against half a point between the best and worst carrier.
- 5am–8am383 flights96.1%
- 8am–11am53 flights94.2%
- 11am–2pm—
- 2pm–5pm381 flights80.2%
- 5pm–8pm—
- 8pm–5am92 flights90.2%
Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 96.1% of the time, against 80.2% for the afternoon window. That is 16 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 383 flights scheduled in it.
Explore
Filter SJU to IAH 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 SJU to IAH, the best departure window is 5am–8am at 96.1% on time and the worst is 2pm–5pm at 80.2%, a wide gap of 15.9 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am96.1%
- 8–11am94.2%
- 11am–2pm—
- 2–5pm80.2%
- 5–8pm—
- 8pm–5am90.2%
best all US flightsScale 60% to 100%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 16 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.
September is the best month on the calendar at 94.1% 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, Wednesday is the strongest day at 92.2% on time and Sunday the weakest at 82.9%, a spread of 9 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 54% of the 5,648 delay minutes carriers reported here, and the remaining four split what is left.
- 54%Late-arriving aircraft
- 26%Carrier
- 20%National Airspace System
54% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,648 reported delay minutes here, that single category outweighs weather by 54 to one. The split is drawn from 5,648 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 96.1% on time here.
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 2.8% 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 84.8% on time across 907 flights, 4 points below 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. 909 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 IAH after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 909 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 88.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 903 completed flights over 12 months sit behind that.
Common questions
SJU to IAH questions
How often is SJU to IAH delayed?
About one flight in nine arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 11.3% of the 909 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is SJU to IAH compared with the rest of the country?
88.7% of flights arrive on time here against a national 77.3%, a difference of 11 points in its favour. That is worth a A+ on this site's grading scale.
What time of day has the fewest delays on SJU to IAH?
The 5am–8am departure window is the strongest at 96.1% on time. The 2pm–5pm window is the weakest at 80.2%, 16 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 October delays on SJU to IAH?
October is the weakest month at 78.6% on time, compared with 94.1% in September. Across the year that is 16 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
- IAH to SJU — the return legseparate record
- Luis Munoz Marin International (SJU) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- SJU to MCO, a related route78.0%
- ORD to IAH, a related route76.0%
- SJU to JFK, a related route77.8%
- United Airlines on-time record89.5%
- Spirit Airlines on-time record72.7%
- The most punctual routes in the US, and the least
- Why the first flight of the morning is statistically safest
Direction matters. SJU to IAH and IAH to SJU 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.