Best time to fly out of Washington Dulles (IAD)

The early-flight folk wisdom holds up at Washington Dulles: departures in the 8–10am band left on time 91% of the time, against 68.7% in the 8–10pm 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 – – 95 88 90 90
6–8am 89 90 91 92 88 87 90
8–10am 90 92 93 92 91 89 90
10am–12pm 87 88 86 87 85 87 88
12–2pm 86 89 90 87 86 87 85
2–4pm 79 81 81 78 78 82 81
4–6pm 76 80 78 75 75 74 74
6–8pm 72 78 76 72 72 69 67
8–10pm 69 71 72 70 69 69 64
10pm–12am 80 85 81 79 78 79 76
fewer left on time more left on time

The steadiest stretch at IAD was 8–10am — 91% of departures left on time across 39,013 flights. The weakest was 8–10pm at 68.7%. 6–8am departures from IAD left on time 89.5% of the time across 14,540 flights; 6–8pm departures, 72.1% across 10,108. That is a gap of 17.4 points, and it is the whole case for the early flight.

The year at IAD

July was the hard month at IAD: 72.1% of departures left on time, across 14,457 flights. October was the easy one at 89%. 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, 83.3%.
Departure on-time share at IAD by calendar month
Month Share departures that left on time Flights
January 82.4% 12,244
February 87.2% 11,540
March 83.3% 13,875
April 87.3% 14,183
May 83.3% 15,613
June 79.4% 14,841
July 72.1% 14,457
August 80.9% 14,638
September 86.6% 13,406
October 89% 14,043
November 87.6% 12,975
December 81.7% 13,135

Airlines at IAD

Every airline with at least 100 departures from IAD, 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 84% 78 min 1% 102,414
Republic Airways 86.6% 79 min 2% 24,444
Delta Air Lines 82.2% 93 min 1.4% 9,338
SkyWest Airlines 80.5% 118 min 1.7% 7,885
Alaska Airlines 76.7% 56 min 1.1% 5,486
PSA Airlines 81.8% 97 min 2.1% 4,164
Southwest Airlines 76% 50 min 0.6% 3,805
American Airlines 77.1% 99 min 2.1% 2,933
Frontier Airlines 71.5% 104 min 2.5% 2,365
Allegiant Air 71.9% 115 min 0.9% 1,313
Endeavor Air 86.7% 64 min 0.5% 641
Envoy Air 93.8% — 0.6% 162

A dash under typical delay means fewer than 30 of that airline’s departures ran 15 minutes late or more — too few to average.

What delays out of IAD were put down to

Airlines file a reason with every arrival running 15 minutes late or more. Across 30,555 flights that departed IAD and ran 15 minutes late or more, the delay minutes break down with 33.3% put down to airline operations and 32.8% to late-arriving aircraft.

Late-arriving aircraft 32.8% Airline operations 33.3% Air traffic & airport volume 24.9% Severe weather 9% Security 0.1%
  • Late-arriving aircraft 32.8%
  • Airline operations 33.3%
  • Air traffic & airport volume 24.9%
  • Severe weather 9%
  • 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 IAD

Of 164,643 scheduled arrivals into IAD, 81.7% reached the gate less than 15 minutes behind schedule. Of the 27,779 arrivals that ran late, 54.5% 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 IAD

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.

IAD in one number

Washington Dulles (IAD)

Rank 37 of 363 US airports by departures. Steadiest stretch of the day: 8–10am. Hardest month: July.

July 2023–June 2026 · 162,888 departures flown

83.3% of departures left on time

Questions about IAD

What is the best time of day to fly out of Washington Dulles?
8–10am. Departures in that band left on time 91% of the time across 39,013 flights, July 2023 through June 2026 — the best of the ten bands in the day. The 8–10pm band was the weakest at 68.7%.
Is the early flight out of IAD really more reliable?
6–8am departures from IAD left on time 89.5% of the time across 14,540 flights; 6–8pm departures, 72.1% across 10,108. That is a gap of 17.4 points, and it is the whole case for the early flight.
What is the worst month to fly out of IAD?
July: 72.1% of the departures that flew left on time, with 14,457 scheduled. October was the other end of the year at 89%. Each figure pools three years of that calendar month.
Which airline is most on time at IAD?
Envoy Air — 93.8% of its 162 departures from IAD left on time. Frontier Airlines sat at the other end at 71.5% over 2,365 flights. Only airlines with at least 100 departures here are ranked.
How often are flights cancelled at IAD?
1.3% 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.