Route reliability record
IAH→PHL
Houston to Philadelphia
- Flights
- 1,832
- Period
- July 2025 to June 2026
- Distance
- 1,325 mi
- Carriers
- 6
This route lands a B, 2 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 close to two hours on average. That is a workable record, not a spotless one. That rests on 1,832 IAH to PHL flights, of which United Airlines flew 891 at 83.0% on time.
Best time to fly IAH to PHL: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 86.8% of the time and Tuesday flights 87.2%, against 79.7% 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
79.7%
Arrivals under 15 minutes late, of 1,792 completed flights
Avg delay
117 min
Across delayed arrivals only, not all flights
Cancelled
2.07%
National rate is 1.81%
Best carrier
United
83.0% on time across 891 flights
These figures cover 1,832 flights between July 2025 and June 2026. Beyond the headline rate, 8.9% 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 IAH to PHL
The two carriers here are closely matched: 5 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 891 | 83.0% | 67 min | 1.01% | B |
| American Airlines | 717 | 78.2% | 159 min | 3.35% | B− |
| Spirit Airlinesthin sample | 42 | 76.9% | 151 min | 4.76% | B− |
| Frontier Airlinesthin sample | 70 | 72.5% | 80 min | 1.43% | C |
| PSA Airlinesthin sample | 92 | 70.8% | 162 min | 2.17% | C |
| Republic Airwaysthin sample | 20 | 60.0% | 150 min | 0.00% | D+ |
American Airlines cancels 3.4% 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.
Flight by flight
Flights on IAH to PHL
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.
Best ways to make this trip
The most reliable ways to fly Houston to Philadelphia
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. IAH → PHLHouston to Philadelphia | United Airlines | 82.2% | 83.0% | 1.01% | 5am–8am, Tue | UA 1663 18:05 |
| 2. IAH → PHLHouston to Philadelphia | American Airlines | 75.6% | 78.2% | 3.35% | 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 14 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am606 flights86.8%
- 8am–11am126 flights82.3%
- 11am–2pm479 flights78.2%
- 2pm–5pm252 flights73.2%
- 5pm–8pm365 flights73.9%
- 8pm–5am4 flights—
Scale runs 65% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 86.8% of the time, against 73.2% for the afternoon window. That is 14 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 606 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 27 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 64.1% on time, 27 points below February, the best at 91.0%. 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 87.2% on time and Sunday the weakest at 73.5%. 14 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Carrier accounts for 46% of the 42,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 46%Carrier
- 38%Late-arriving aircraft
- 13%National Airspace System
- 3%Extreme weather
38% 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 42,000 reported delay minutes here, that single category outweighs weather by 11 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 42,313 reported delay minutes.
The largest share of delay minutes, 46%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 20,000 of the 42,000 delay minutes reported here.
Cancellations sit at 2.07% against a national 1.81%, which is ordinary. Diversions add another 0.11%.
Connections and stage length
What a delay here actually costs
8.9% 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 close to two hours, 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 80.1% on time across 1,829 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 1,832 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 PHL 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 91.0% on time and July 64.1%, a swing of 27 points. If the dates move at all, move them out of July before you think about anything else. 1,792 completed flights over 12 months sit behind that.
Common questions
IAH to PHL questions
How often is IAH to PHL 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 20.3% of the 1,832 flights in this analysis, against 22.4% nationally. Delayed flights are late by close to two hours on average.
Which airline is most reliable on IAH to PHL?
United Airlines leads at 83.0% on time across 891 flights. American Airlines is at the other end on 78.2%, a gap of 5 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 IAH to PHL?
The 5am–8am departure window is the strongest at 86.8% on time. The 2pm–5pm window is the weakest at 73.2%, 14 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 IAH to PHL?
July is the weakest month at 64.1% on time, compared with 91.0% in February. Across the year that is 27 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
- PHL to IAH — the return legseparate record
- George Bush Intercontinental (IAH) delay statistics
- Philadelphia International (PHL) delay statistics
- United Airlines on IAH to PHL83.0%
- American Airlines on IAH to PHL78.2%
- IAH to ORD, a related route74.8%
- ATL to PHL, a related route74.9%
- IAH to DFW, a related route75.0%
- United Airlines on-time record83.0%
- American Airlines on-time record78.2%
- Spirit Airlines on-time record76.9%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. IAH to PHL and PHL 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.