Route reliability record
RDU→IAH
Raleigh to Houston
- Flights
- 906
- Period
- July 2025 to June 2026
- Distance
- 1,042 mi
- Carriers
- 3
This route lands a B, 6 points better than the national rate of 77.6%. About one flight in six 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 906 RDU to IAH flights, with a median arrival 11 minutes early.
Best time to fly RDU to IAH: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 91.9% of the time and Tuesday flights 87.9%, against 83.5% for the route overall.
Set against the rest of the country, this route's record is 6 points better than the US average of 77.6%. That gap is worth roughly 59 fewer late arrivals for every thousand flights.
Key figures
On time
83.5%
Arrivals under 15 minutes late, of 895 completed flights
Avg delay
83 min
Across delayed arrivals only, not all flights
Cancelled
1.21%
National rate is 1.81%
Best carrier
United
86.6% on time across 700 flights
These figures cover 906 flights between July 2025 and June 2026. The median arrival is 11 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.
Carrier by carrier
Which airline is most reliable on RDU 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 |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| United Airlines | 700 | 86.6% | 75 min | 0.86% | A+ |
| Frontier Airlinesthin sample | 205 | 72.5% | 96 min | 2.44% | C |
Flight by flight
Flights on RDU 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.
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 22 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am364 flights91.9%
- 8am–11am96 flights82.1%
- 11am–2pm41 flights82.9%
- 2pm–5pm143 flights88.7%
- 5pm–8pm237 flights69.7%
- 8pm–5am25 flights—
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 91.9% of the time, against 69.7% for the evening window. That is 22 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 364 flights scheduled in it.
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 56.9% on time, 36 points below September, the best at 93.2%. 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. March was the busiest month here, with 100 flights.
Across the week, Tuesday is the strongest day at 87.9% on time and Sunday the weakest at 80.8%. 7 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. Late-arriving aircraft accounts for 43% of the 12,000 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.
- 43%Late-arriving aircraft
- 32%National Airspace System
- 22%Carrier
- 3%Extreme weather
43% 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 12,000 reported delay minutes here, that single category outweighs weather by 14 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 12,255 reported delay minutes.
32% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 3,973 minutes out of 12,000, against a national NAS share of 21%.
Cancellations sit at 1.21% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here actually costs
6.4% 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 1,042 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 82.2% on time across 906 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 906 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. 906 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 83.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 895 completed flights over 12 months sit behind that.
Common questions
RDU to IAH questions
How often is RDU to IAH delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 16.5% of the 906 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
How reliable is RDU to IAH compared with the rest of the country?
83.5% of flights arrive on time here against a national 77.6%, a difference of 6 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on RDU to IAH?
The 5am–8am departure window is the strongest at 91.9% on time. The 5pm–8pm window is the weakest at 69.7%, 22 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 RDU to IAH?
July is the weakest month at 56.9% on time, compared with 93.2% in September. 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
- IAH to RDU — the return legseparate record
- Raleigh-Durham International (RDU) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- United Airlines on RDU to IAH86.6%
- Frontier Airlines on RDU to IAH72.5%
- RDU to ATL, a related route87.6%
- ORD to IAH, a related route75.0%
- RDU to ORD, a related route74.4%
- SkyWest Airlines on-time record100.0%
- United Airlines on-time record86.6%
- Frontier Airlines on-time record72.5%
- 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. RDU to IAH and IAH to RDU 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.