Route reliability record
IAH→PHL
Houston to Philadelphia
- Flights
- 1,878
- Period
- September 2025 to August 2026
- Distance
- 1,325 mi
- Carriers
- 5
This route lands a B, 2 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 an hour and a half on average. That rests on 1,878 IAH to PHL flights, of which United Airlines flew 954 at 81.5% on time.
Best time to fly IAH to PHL: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 86.7% of the time and Tuesday flights 83.5%, against 78.8% 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
78.8%
Arrivals under 15 minutes late, of 1,841 completed flights
Avg delay
90 min
Across delayed arrivals only, not all flights
Cancelled
1.86%
National rate is 1.89%
Best carrier
United
81.5% on time across 954 flights
These figures cover 1,878 flights between September 2025 and August 2026. Beyond the headline rate, 9.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
Fare search by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Carrier by carrier
Which airline is most reliable on IAH to PHL
The two carriers here are closely matched: 4 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 | 954 | 81.5% | 69 min | 0.94% | B+ |
| American Airlines | 724 | 77.6% | 97 min | 3.18% | B− |
| Frontier Airlinesthin sample | 72 | 71.8% | 85 min | 1.39% | C |
| PSA Airlinesthin sample | 92 | 70.8% | 162 min | 2.17% | C |
| Republic Airwaysthin sample | 36 | 63.9% | 147 min | 0.00% | D+ |
American Airlines cancels 3.2% 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.
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
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 | 80.7% | 81.5% | 0.94% | 5am–8am, Sat | UA 1663 18:05 |
| 2. IAH → PHLHouston to Philadelphia | American Airlines | 75.1% | 77.6% | 3.18% | 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 16 points, against 4 points between the best and worst carrier.
- 5am–8am622 flights86.7%
- 8am–11am102 flights82.2%
- 11am–2pm495 flights77.2%
- 2pm–5pm301 flights70.3%
- 5pm–8pm354 flights73.1%
- 8pm–5am4 flights—
Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 86.7% of the time, against 70.3% 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 622 flights scheduled in it.
Explore
Filter IAH to PHL 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 PHL, the best departure window is 5am–8am at 86.7% on time and the worst is 2pm–5pm at 70.3%, a wide gap of 16.4 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am86.7%
- 8–11am82.2%
- 11am–2pm77.2%
- 2–5pm70.3%
- 5–8pm73.1%
- 8pm–5am—
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 36 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 54.6% on time, 36 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 83.5% on time and Sunday the weakest at 74.2%, a spread of 9 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 35,000 reported delay minutes.
- 41%Late-arriving aircraft
- 34%Carrier
- 22%National Airspace System
- 4%Extreme weather
41% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 35,000 reported delay minutes here, that single category outweighs weather by 12 to one. The split is drawn from 35,078 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 86.7% on time here.
Cancellations sit at 1.86% against a national 1.89%, which is ordinary. Diversions add another 0.11%.
Connections and stage length
What a delay here actually costs
9.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
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.
The return leg runs 81.7% on time across 1,878 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 1,878 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 54.6%, a swing of 36 points. If the dates move at all, move them out of July before you think about anything else. 1,841 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 21.2% of the 1,878 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on IAH to PHL?
United Airlines leads at 81.5% on time across 954 flights. American Airlines is at the other end on 77.6%, a gap of 4 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 86.7% on time. The 2pm–5pm window is the weakest at 70.3%, 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 July delays on IAH to PHL?
July is the weakest month at 54.6% on time, compared with 91.0% in February. Across the year that is 36 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 PHL81.5%
- American Airlines on IAH to PHL77.6%
- IAH to ORD, a related route75.1%
- ATL to PHL, a related route74.6%
- IAH to DFW, a related route76.4%
- United Airlines on-time record81.5%
- American Airlines on-time record77.6%
- Frontier Airlines on-time record71.8%
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
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.
Embed IAH to PHL’s on-time badge on your site
Paste this into a web page. The badge shows the current on-time rate, cancellation rate and grade, and updates every month. Preview it, or build a badge for another route or airport.
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.