Houston, TX · departure reliability

IAH

George Bush Intercontinental

Departures: 119,193
Period: June 2025 to May 2026
Carriers: 10
US rank: #17 by volume

Terminal building and aircraft stands at a US airport

Houston

George Bush Intercontinental lands a B, level with the national rate of 77.4%. Roughly one flight in five arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 119,193 flights, of which Delta Air Lines flew 8,344 at 80.3% on time.

Delta Air Lines is the most reliable of the ten carriers covered here at 80.3% on time across 8,344 flights.

On time

78.0%

Departures arriving under 15 minutes late at their destination

Avg delay

78 min

Across delayed flights only

Cancelled

1.27%

National rate is 1.80%

Best carrier

Delta

80.3% on time here

These figures cover 119,000 flights between June 2025 and May 2026. Beyond the headline rate, 8.7% 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 airlines run best out of IAH

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 80.3% of the time; JetBlue Airways manages 60.3%. Sample sizes sit next to every figure, because a two-point gap across 493 flights means less than a ten-point one.

On-time performance by carrier departing IAH
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	73,829	79.3%	67 min	0.80%	B+
SkyWest Airlines	14,441	76.2%	94 min	1.45%	B
Delta Air Lines	8,344	80.3%	86 min	1.89%	B
American Airlines	7,653	76.8%	132 min	2.61%	B
Spirit Airlines	6,056	74.0%	74 min	2.77%	C
Frontier Airlines	4,514	69.1%	89 min	1.71%	C
Envoy Air	1,489	76.1%	80 min	2.42%	B
Alaska Airlines	1,208	77.2%	56 min	1.16%	B
Republic Airways	874	74.2%	74 min	3.89%	C−
JetBlue Airways	493	60.3%	80 min	2.23%	D

Republic Airways cancels 3.9% 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.

Route by route

Busiest routes out of IAH

Route-level records vary far more than the airport average. These are the 25 busiest departures from IAH, each with its own on-time rate against the airport-wide 78.0%.

Busiest routes from IAH by flight volume
Route	Flights	On time	Avg delay	Cancelled	Grade
IAH to ORD · Chicago	6,063	74.7%	82 min	1.45%	C
IAH to DFW · Dallas-Fort Worth	5,773	74.8%	98 min	2.86%	C
IAH to LAX · Los Angeles	5,294	83.0%	67 min	0.68%	B+
IAH to ATL · Atlanta	4,900	77.1%	71 min	2.02%	B
IAH to DEN · Denver	4,632	81.2%	71 min	0.30%	B+
IAH to LGA · New York	4,074	71.6%	81 min	2.85%	C
IAH to MIA · Miami	3,764	77.6%	90 min	1.28%	B
IAH to EWR · Newark	3,764	74.2%	74 min	1.91%	C
IAH to MCO · Orlando	3,709	80.6%	84 min	1.11%	B
IAH to SFO · San Francisco	3,595	79.2%	71 min	0.53%	B+
IAH to LAS · Las Vegas	3,485	82.0%	74 min	0.80%	B+
IAH to DCA · Washington	3,116	75.0%	69 min	1.77%	B
IAH to MSY · New Orleans	2,997	82.6%	68 min	0.53%	B+
IAH to PHX · Phoenix	2,912	78.2%	83 min	1.00%	B
IAH to FLL · Fort Lauderdale	2,840	79.6%	69 min	1.16%	B
IAH to AUS · Austin	2,674	78.5%	69 min	1.01%	B
IAH to SAT · San Antonio	2,452	82.5%	64 min	0.86%	B+
IAH to CLT · Charlotte	2,363	78.7%	111 min	2.16%	B
IAH to DTW · Detroit	2,144	78.8%	78 min	1.31%	B
IAH to SEA · Seattle	2,107	76.2%	58 min	0.90%	B+
IAH to BOS · Boston	2,035	72.2%	74 min	1.43%	C
IAH to SLC · Salt Lake City	1,965	82.4%	77 min	0.61%	B+
IAH to IAD · Washington	1,862	79.6%	62 min	0.59%	B+
IAH to MSP · Minneapolis	1,845	77.2%	83 min	1.14%	B
IAH to PHL · Philadelphia	1,805	80.1%	114 min	2.22%	B

Departure window

The best time of day to leave IAH

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 19 points, against 20 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am19,666 flights88.5%
8am–11am16,921 flights83.0%
11am–2pm19,128 flights79.5%
2pm–5pm21,130 flights75.4%
5pm–8pm21,856 flights69.7%
8pm–5am20,492 flights73.7%

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 88.5% of the time, against 69.7% for the evening window. That is 19 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.

Across the year

When IAH runs late

IAH's year swings by 21 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.

Darker means more delays. Figures are on-time percentages.January best, June worst

June is the worst month at 65.2% on time, 21 points below January, the best at 85.7%. 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.

Across the week, Tuesday is the strongest day at 82.9% on time and Sunday the weakest at 74.2%. 9 points is a smaller lever than departure hour, but it is free.

Delay causes

Why IAH 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 2.01 million reported delay minutes.

Late-arriving aircraft
38%
Carrier
33%
National Airspace System
22%
Extreme weather
8%
Security
0%

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 2.01 million reported delay minutes here, that single category outweighs weather by 5 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 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 88.5% on time here.

Cancellations sit at 1.27% against a national 1.80%, which is ordinary. Diversions add another 0.27%.

8.7% of arrivals land an hour or more late, close to the national 8.2%. 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 are the a little over an hour kind, which a normal layover absorbs.

119,193 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.

What to do with this

Flying out of IAH

Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 85.7% on time and June 65.2%, a swing of 21 points. If the dates move at all, move them out of June before you think about anything else.

Common questions

IAH delay questions

How often is Houston (IAH) delayed?

Roughly one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.0% of the 119,193 flights in this analysis, against 22.6% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on Houston (IAH)?

Delta Air Lines leads at 80.3% on time across 8,344 flights. JetBlue Airways is at the other end on 60.3%, a gap of 20 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 Houston (IAH)?

The 5am–8am departure window is the strongest at 88.5% on time. The 5pm–8pm window is the weakest at 69.7%, 19 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 June delays on Houston (IAH)?

June is the weakest month at 65.2% on time, compared with 85.7% in January. Across the year that is 21 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.

Key figures