Airport month record

IAHSEP

George Bush Intercontinental in September 2025

Departures: 9,493
Month: September 2025
National, same month: 83.4%
Carriers: 10

Historical statistics for September 2025, not live status or a forecast for this year’s September. For today’s conditions at IAH, see live FAA status.

IAH in September earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 2 points better than the national rate of 83.4%. When something does go wrong the average delay runs a little over an hour. That rests on 9,493 flights, of which Delta Air Lines flew 686 at 91.9% on time.

Delta Air Lines is the most reliable of the five carriers covered here at 91.9% on time across 686 flights.

On time

85.6%

Arrivals under 15 minutes late, of 9,462 completed departures

Avg delay

69 min

Across delayed arrivals only, not all flights

Cancelled

0.20%

Nationally in September: 0.51%

Whole year

78.4%

IAH across all twelve months

These figures cover 9,493 departures from George Bush Intercontinental in September 2025. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.

Against the year

September next to IAH's other months

Against IAH's own year, September ran 7 points better than the twelve-month rate of 78.4%, which makes it number two of twelve months, best first. Cancellations were unusually low for IAH in September, at 0.20% against 1.14% across the year. Either side of it, August ran 74.1% on time and October 80.7%, so a trip moved by a few weeks would have landed in a worse stretch.

IAH month by month
Month	Flights	On time	Avg delay	Cancelled	Grade
July 2025	10,311	68.8%	88 min	1.74%	C
August 2025	9,889	74.1%	74 min	0.87%	C+
September 2025 (this page)	9,493	85.6%	69 min	0.20%	A+
October 2025	10,247	80.7%	65 min	0.30%	B+
November 2025	10,022	78.2%	73 min	1.06%	B
December 2025	9,971	79.4%	71 min	0.60%	B+
January 2026	9,656	85.7%	74 min	3.07%	A−
February 2026	8,976	85.6%	68 min	1.06%	A
March 2026	10,492	76.4%	95 min	2.89%	B
April 2026	10,022	80.4%	69 min	0.57%	B+
May 2026	10,105	77.1%	73 min	0.46%	B+
June 2026	9,903	69.9%	79 min	0.75%	C+

Departure window

The best time of day to leave IAH in September

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 13 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am1,582 flights93.1%
8am–11am1,381 flights89.3%
11am–2pm1,546 flights87.1%
2pm–5pm1,646 flights82.9%
5pm–8pm1,737 flights80.1%
8pm–5am1,601 flights82.5%

Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 93.1% of the time, against 80.1% for the evening window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 1,737 flights scheduled in it.

Across the week, Tuesday is the strongest day at 89.6% on time and Wednesday the weakest at 82.5%. 7 points is a smaller lever than departure hour, but it is free.

Carrier by carrier

Which airlines ran best at IAH in September

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 91.9% of the time; American Airlines manages 83.1%. Sample sizes sit next to every figure, because a two-point gap across 618 flights means less than a ten-point one.

Carriers at IAH in September 2025
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	5,940	85.4%	52 min	0.07%	A+
SkyWest Airlines	936	88.2%	79 min	0.00%	A+
Delta Air Lines	686	91.9%	69 min	0.29%	A+
American Airlines	618	83.1%	198 min	1.46%	B
Spirit Airlines	618	85.3%	75 min	0.49%	A+
Frontier Airlinesthin sample	309	82.1%	86 min	0.00%	B+
Envoy Airthin sample	157	77.6%	55 min	0.64%	B+
Alaska Airlinesthin sample	111	89.2%	41 min	0.00%	A+
Republic Airwaysthin sample	82	80.5%	51 min	0.00%	B+
JetBlue Airwaysthin sample	32	37.5%	71 min	0.00%	F+

Delta leads American by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Route by route

Busiest routes out of IAH in September

Routes from IAH in September 2025
Route	Flights	On time	Avg delay	Cancelled	Grade
IAH to ORD · Chicago	531	85.8%	75 min	0.19%	A+
IAH to DFW · Dallas-Fort Worth	498	80.6%	87 min	1.61%	B
IAH to LAX · Los Angeles	440	86.6%	56 min	0.00%	A+
IAH to ATL · Atlanta	384	91.1%	39 min	0.26%	A+
IAH to DEN · Denver	383	81.9%	43 min	0.26%	B+
IAH to LGA · New York	369	85.8%	47 min	0.27%	A+
IAH to EWR · Newarkthin sample	326	81.9%	70 min	0.00%	B+
IAH to SFO · San Franciscothin sample	289	89.3%	47 min	0.00%	A+
IAH to MSY · New Orleansthin sample	280	91.8%	44 min	0.00%	A+
IAH to MIA · Miamithin sample	276	81.1%	123 min	0.36%	B+
IAH to DCA · Washingtonthin sample	272	80.5%	50 min	0.00%	B+
IAH to MCO · Orlandothin sample	271	90.0%	102 min	0.00%	A+
IAH to LAS · Las Vegasthin sample	255	83.1%	48 min	0.00%	B+
IAH to AUS · Austinthin sample	237	87.8%	42 min	0.00%	A+
IAH to SAT · San Antoniothin sample	229	87.3%	56 min	0.00%	A+
IAH to SEA · Seattlethin sample	199	85.9%	47 min	0.00%	A+
IAH to FLL · Fort Lauderdalethin sample	197	89.3%	69 min	0.51%	A+
IAH to IAD · Washingtonthin sample	193	92.7%	64 min	0.00%	A+
IAH to PHX · Phoenixthin sample	191	82.4%	151 min	0.52%	B+
IAH to DTW · Detroitthin sample	180	89.4%	57 min	0.00%	A+
IAH to CLT · Charlottethin sample	175	87.9%	330 min	0.57%	A+
IAH to SLC · Salt Lake Citythin sample	161	90.7%	48 min	0.00%	A+
IAH to BOS · Bostonthin sample	158	57.3%	75 min	0.63%	D+
IAH to MSP · Minneapolisthin sample	137	87.5%	84 min	0.00%	A+
IAH to PHL · Philadelphiathin sample	137	87.5%	78 min	0.00%	A+

Delay causes

What held IAH up in September

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 94,000 reported delay minutes.

Carrier
38%
Late-arriving aircraft
35%
National Airspace System
23%
Extreme weather
3%
Security
0%

35% 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 94,000 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 93,818 reported delay minutes.

Cancellations are rare at 0.20%, below the national 0.51% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Badly late arrivals are rare here: only 4.6% land an hour or more behind schedule, against 5.4% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

What to do with this

Flying from IAH in September

For a September trip through IAH: this is one of the better months to be flying from here, 85.6% on time with 0.20% cancelled. That is a base rate for the month as a whole; a single storm can still spoil a particular day.

George Bush Intercontinental (IAH), the whole year
IAH in July68.8%
IAH in August74.1%
IAH in October80.7%
IAH in November78.2%
IAH in December79.4%
IAH in January85.7%
IAH in February85.6%
IAH in March76.4%
IAH in April80.4%
IAH in May77.1%
IAH in June69.9%

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.

Key figures