Route reliability record
PHL→IAH
Philadelphia to Houston
- Flights
- 1,829
- Period
- July 2025 to June 2026
- Distance
- 1,325 mi
- Carriers
- 6
This route lands a B, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 1,829 PHL to IAH flights, of which United Airlines flew 891 at 86.9% on time.
Best time to fly PHL to IAH: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 87.6% of the time and Tuesday flights 86.2%, against 80.1% for the route overall.
The US average over the same twelve months is 77.6%, 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
80.1%
Arrivals under 15 minutes late, of 1,789 completed flights
Avg delay
83 min
Across delayed arrivals only, not all flights
Cancelled
1.97%
National rate is 1.81%
Best carrier
United
86.9% on time across 891 flights
These figures cover 1,829 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on PHL to IAH
The choice of carrier is not cosmetic here. United Airlines arrives on time 86.9% of the time; American Airlines manages 74.1%. Sample sizes sit next to every figure, because a two-point gap across 714 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 891 | 86.9% | 81 min | 1.01% | A |
| Republic Airwaysthin sample | 20 | 80.0% | 89 min | 0.00% | B+ |
| PSA Airlinesthin sample | 92 | 77.3% | 77 min | 2.17% | B |
| American Airlines | 714 | 74.1% | 87 min | 3.08% | C− |
| Frontier Airlinesthin sample | 70 | 68.1% | 60 min | 1.43% | C |
| Spirit Airlinesthin sample | 42 | 60.0% | 79 min | 4.76% | D− |
American Airlines cancels 3.1% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Best ways to make this trip
The most reliable ways to fly Philadelphia to Houston
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. PHL → IAHPhiladelphia to Houston | United Airlines | 86.0% | 86.9% | 1.01% | 5am–8am, Tue | — |
| 2. PHL → IAHPhiladelphia to Houston | American Airlines | 71.8% | 74.1% | 3.08% | 8am–11am, Tue | — |
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 21 points, against 13 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am154 flights87.6%
- 8am–11am590 flights86.2%
- 11am–2pm425 flights80.2%
- 2pm–5pm29 flights—
- 5pm–8pm474 flights75.9%
- 8pm–5am157 flights66.7%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 87.6% of the time, against 66.7% for the overnight window. That is 21 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 590 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 25 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.
July is the worst month at 66.9% on time, 25 points below February, the best at 91.8%. 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. June was the busiest month here, with 187 flights.
Across the week, Tuesday is the strongest day at 86.2% on time and Sunday the weakest at 76.6%. 10 points is a smaller lever than departure hour, but it is free.
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 29,000 reported delay minutes.
- 37%Late-arriving aircraft
- 31%Carrier
- 28%National Airspace System
- 4%Extreme weather
- 0%Security
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 29,000 reported delay minutes here, that single category outweighs weather by 9 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 29,423 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 87.6% on time here.
Cancellations sit at 1.97% against a national 1.81%, which is ordinary. Diversions add another 0.22%.
Connections and stage length
What a delay here actually costs
8.2% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last an hour and a half, which a normal layover absorbs.
The 1,325 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 79.7% on time across 1,832 flights, within half a point 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 1,829 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 IAH 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 91.8% on time and July 66.9%, a swing of 25 points. If the dates move at all, move them out of July before you think about anything else. 1,789 completed flights over 12 months sit behind that.
Common questions
PHL to IAH questions
How often is PHL to IAH 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 19.9% of the 1,829 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on PHL to IAH?
United Airlines leads at 86.9% on time across 891 flights. American Airlines is at the other end on 74.1%, a gap of 13 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on PHL to IAH?
The 5am–8am departure window is the strongest at 87.6% on time. The 8pm–5am window is the weakest at 66.7%, 21 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 July delays on PHL to IAH?
July is the weakest month at 66.9% on time, compared with 91.8% in February. Across the year that is 25 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 PHL — the return legseparate record
- Philadelphia International (PHL) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- United Airlines on PHL to IAH86.9%
- American Airlines on PHL to IAH74.1%
- PHL to ATL, a related route79.2%
- ORD to IAH, a related route75.0%
- PHL to MCO, a related route72.4%
- United Airlines on-time record86.9%
- Republic Airways on-time record80.0%
- PSA Airlines on-time record77.3%
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
Direction matters. PHL to IAH and IAH to PHL 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.