Airport month record

IAHMAY

George Bush Intercontinental in May 2026

Departures: 10,105
Month: May 2026
National, same month: 78.6%
Carriers: 10

Historical statistics for May 2026, not live status or a forecast for this year’s May. For today’s conditions at IAH, see live FAA status.

IAH in May lands a B+, 2 points worse than the national rate of 78.6%. Roughly one flight in four arrives 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 10,105 flights, of which Delta Air Lines flew 767 at 79.7% on time.

Delta Air Lines is the most reliable of the five carriers covered here at 79.7% on time across 767 flights.

On time

77.1%

Arrivals under 15 minutes late, of 10,029 completed departures

Avg delay

73 min

Across delayed arrivals only, not all flights

Cancelled

0.46%

Nationally in May: 0.92%

Whole year

78.4%

IAH across all twelve months

These figures cover 10,105 departures from George Bush Intercontinental in May 2026. 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

May next to IAH's other months

Against IAH's own year, May ran about a point worse than the twelve-month rate of 78.4%, which makes it number eight of twelve months, best first. Cancellations were unusually low for IAH in May, at 0.46% against 1.14% across the year. Either side of it, April ran 80.4% on time and June 69.9%, so this month sits in line with its neighbours.

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	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 (this page)	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 May

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 15 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am1,565 flights87.5%
8am–11am1,572 flights79.8%
11am–2pm1,653 flights75.6%
2pm–5pm1,775 flights74.3%
5pm–8pm1,822 flights72.4%
8pm–5am1,718 flights74.6%

Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 87.5% of the time, against 72.4% for the evening window. That is 15 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 1,822 flights scheduled in it.

Across the week, Tuesday is the strongest day at 84.0% on time and Friday the weakest at 69.5%. 15 points is a smaller lever than departure hour, but it is free.

Carrier by carrier

Which airlines ran best at IAH in May

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 79.7% of the time; Frontier Airlines manages 71.2%. Sample sizes sit next to every figure, because a two-point gap across 564 flights means less than a ten-point one.

Carriers at IAH in May 2026
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	6,414	78.6%	62 min	0.30%	B+
SkyWest Airlines	1,226	72.0%	89 min	0.57%	C+
Delta Air Lines	767	79.7%	69 min	0.39%	B+
American Airlines	697	76.5%	110 min	1.00%	B
Frontier Airlines	564	71.2%	91 min	0.00%	C+
Envoy Airthin sample	127	69.6%	119 min	1.57%	C
Alaska Airlinesthin sample	107	86.0%	42 min	0.00%	A+
PSA Airlinesthin sample	84	70.4%	91 min	2.38%	C
JetBlue Airwaysthin sample	53	61.5%	100 min	1.89%	D
Republic Airwaysthin sample	50	81.2%	73 min	0.00%	B+

Delta leads Frontier 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 May

Routes from IAH in May 2026
Route	Flights	On time	Avg delay	Cancelled	Grade
IAH to ORD · Chicago	539	76.0%	66 min	0.00%	B+
IAH to DFW · Dallas-Fort Worth	518	71.4%	120 min	3.09%	C−
IAH to ATL · Atlanta	446	70.0%	71 min	0.45%	C+
IAH to LAX · Los Angeles	422	84.1%	61 min	0.24%	B+
IAH to DEN · Denver	412	83.0%	58 min	0.00%	B+
IAH to LGA · New Yorkthin sample	347	78.1%	66 min	1.44%	B
IAH to SFO · San Franciscothin sample	307	66.4%	57 min	0.00%	C+
IAH to MIA · Miamithin sample	294	76.9%	76 min	0.00%	B+
IAH to DCA · Washingtonthin sample	289	74.4%	65 min	0.69%	C+
IAH to EWR · Newarkthin sample	288	82.0%	61 min	1.04%	B
IAH to MCO · Orlandothin sample	274	83.8%	76 min	0.36%	B+
IAH to LAS · Las Vegasthin sample	263	81.7%	87 min	0.38%	B+
IAH to PHX · Phoenixthin sample	256	75.0%	57 min	0.00%	B+
IAH to MSY · New Orleansthin sample	233	79.7%	86 min	0.00%	B+
IAH to AUS · Austinthin sample	228	75.4%	66 min	1.32%	B
IAH to CLT · Charlottethin sample	215	78.6%	114 min	0.00%	B+
IAH to SAT · San Antoniothin sample	185	81.6%	63 min	0.00%	B+
IAH to SEA · Seattlethin sample	183	88.0%	55 min	0.00%	A+
IAH to DTW · Detroitthin sample	182	76.8%	50 min	0.55%	B+
IAH to MSP · Minneapolisthin sample	180	82.2%	52 min	0.00%	B+
IAH to BOS · Bostonthin sample	178	72.5%	62 min	0.00%	C+
IAH to PHL · Philadelphiathin sample	167	80.8%	83 min	0.00%	B+
IAH to IAD · Washingtonthin sample	166	86.1%	52 min	0.60%	A+
IAH to FLL · Fort Lauderdalethin sample	158	75.9%	66 min	0.00%	B+
IAH to SLC · Salt Lake Citythin sample	149	79.1%	74 min	0.67%	B+

Delay causes

What held IAH up in May

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 168,000 reported delay minutes.

Late-arriving aircraft
42%
Carrier
31%
National Airspace System
19%
Extreme weather
8%
Security
0%

42% 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 168,000 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 split is drawn from 168,386 reported delay minutes.

Cancellations are rare at 0.46%, below the national 0.92% 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.

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.0% of arrivals land a full hour or more behind schedule, against 7.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

What to do with this

Flying from IAH in May

For a May trip through IAH: expect 77.1% on time and 0.46% cancelled, going by May 2026. The 5am–8am window was the strongest part of the day.

George Bush Intercontinental (IAH), the whole year
IAH in July68.8%
IAH in August74.1%
IAH in September85.6%
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 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