Best time to fly out of George Bush (IAH)

The early-flight folk wisdom holds up at George Bush: departures in the Before 6am band left on time 91.3% of the time, against 69.1% in the 6–8pm band. These are historical odds, not forecasts. The records say what happened on this schedule over three years; they know nothing about tomorrow’s thunderstorm.

Data through June 2026 · Bureau of Transportation Statistics

On-time rate by hour and day

On this page, “on time” means a departure that pushed back less than 15 minutes behind its scheduled time — the Bureau of Transportation Statistics definition, and the one airlines are held to.

Share of departures that left on time, by hour band and day of week.
Departure time MonTueWedThuFriSatSun
Before 6am 91 92 93 93 91 89 91
6–8am 88 90 92 91 89 89 89
8–10am 84 87 86 84 84 84 84
10am–12pm 79 83 81 80 80 78 78
12–2pm 77 82 82 79 77 79 77
2–4pm 74 80 77 75 73 76 74
4–6pm 72 76 76 71 70 75 68
6–8pm 69 74 73 68 67 68 66
8–10pm 70 76 76 70 68 70 67
10pm–12am 73 80 80 72 73 75 72
fewer left on time more left on time

The steadiest stretch at IAH was Before 6am — 91.3% of departures left on time across 9,524 flights. The weakest was 6–8pm at 69.1%. 6–8am departures from IAH left on time 89.7% of the time across 46,014 flights; 6–8pm departures, 69.1% across 62,472. That is a gap of 20.6 points, and it is the whole case for the early flight.

The year at IAH

July was the hard month at IAH: 65.4% of departures left on time, across 30,469 flights. October was the easy one at 84%. Each month pools three years of that month, so a single bad week does not decide it.

Share of departures that left on time, by calendar month. Best month in green, worst in amber. The hairline sits at the overall rate, 77.5%.
Departure on-time share at IAH by calendar month
Month Share departures that left on time Flights
January 79.1% 27,839
February 83.8% 25,910
March 77.5% 29,898
April 80% 28,820
May 70.2% 30,468
June 68.4% 29,940
July 65.4% 30,469
August 76.5% 29,959
September 83.1% 28,278
October 84% 30,393
November 83.6% 28,617
December 79.7% 28,619

Airlines at IAH

Every airline with at least 100 departures from IAH, busiest first. These are that airline’s departures from this airport only — its record across the country sits on its own page.

Airline Left on time Typical delay Cancelled Departures
United Airlines 77.9% 69 min 1.2% 212,194
SkyWest Airlines 78.3% 99 min 1.8% 40,081
Delta Air Lines 80.1% 84 min 1.3% 24,255
Spirit Airlines 75.3% 73 min 2.1% 22,948
American Airlines 76.3% 119 min 2.5% 21,771
Frontier Airlines 67.9% 92 min 2.3% 10,944
Southwest Airlines 82.3% 61 min 1.1% 5,853
Envoy Air 79% 82 min 2.6% 4,239
Alaska Airlines 78.3% 53 min 1.4% 3,027
JetBlue Airways 58.4% 105 min 2% 2,114
Republic Airways 76.9% 89 min 4.2% 1,294
PSA Airlines 72.4% 145 min 3.9% 490

Spirit Airlines (through May 2026) stopped filing before June 2026. Its row covers a shorter run of months than the rest of the table, so its figure is not set against the others anywhere on this page.

What delays out of IAH were put down to

Airlines file a reason with every arrival running 15 minutes late or more. Across 76,946 flights that departed IAH and ran 15 minutes late or more, the delay minutes break down with 38.7% put down to late-arriving aircraft and 33.7% to airline operations.

Late-arriving aircraft 38.7% Airline operations 33.7% Air traffic & airport volume 19.8% Severe weather 7.7% Security 0.1%
  • Late-arriving aircraft 38.7%
  • Airline operations 33.7%
  • Air traffic & airport volume 19.8%
  • Severe weather 7.7%
  • Security 0.1%

Late-arriving aircraft is the knock-on category: the plane came in late, so it went out late again. It is why a 7am problem in Newark is still a problem in Denver at dinnertime, and why it is usually the biggest slice on the bar.

If you are connecting through IAH

Of 349,231 scheduled arrivals into IAH, 78.6% reached the gate less than 15 minutes behind schedule. Of the 68,278 arrivals that ran late, 52.5% were no more than 45 minutes behind — which is the difference between a tight connection and a new boarding pass.

Work out a specific layover — pick the airport and the minutes you have, and the tool reads the same arrival records back as a share.

Busiest routes out of IAH

Ranked by flights, with the share that arrived on time at the far end. Where a route carries enough flights for a page of its own the chip goes there; otherwise it goes to the destination airport.

IAH in one number

George Bush (IAH)

Rank 18 of 363 US airports by departures. Steadiest stretch of the day: Before 6am. Hardest month: July.

July 2023–June 2026 · 344,089 departures flown

77.5% of departures left on time

Questions about IAH

What is the best time of day to fly out of George Bush?
Before 6am. Departures in that band left on time 91.3% of the time across 9,524 flights, July 2023 through June 2026 — the best of the ten bands in the day. The 6–8pm band was the weakest at 69.1%.
Is the early flight out of IAH really more reliable?
6–8am departures from IAH left on time 89.7% of the time across 46,014 flights; 6–8pm departures, 69.1% across 62,472. That is a gap of 20.6 points, and it is the whole case for the early flight.
What is the worst month to fly out of IAH?
July: 65.4% of the departures that flew left on time, with 30,469 scheduled. October was the other end of the year at 84%. Each figure pools three years of that calendar month.
Which airline is most on time at IAH?
Southwest Airlines — 82.3% of its 5,853 departures from IAH left on time. JetBlue Airways sat at the other end at 58.4% over 2,114 flights. Only airlines with at least 100 departures here are ranked. Airlines that stopped filing before June 2026 are left out of the ranking — their figures cover a shorter run of months than the rest of the table.
How often are flights cancelled at IAH?
1.5% of scheduled departures were cancelled over July 2023 through June 2026. Cancellations are counted against everything scheduled, not against everything that flew — a rate that looks small still adds up to real people in a rebooking line.