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Route on-time record

IAD to SEA: most on-time flights and the best time to fly

Dulles (Washington Dulles International Airport) to Seattle (Seattle–Tacoma International Airport). 1,926 nonstop flights in Jun 2025 to May 2026, 76% arrived within 15 minutes and 1.0% were cancelled. The most reliable flight number was United 2241 at 1:15 PM.

Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.

IAD → SEA

Dulles to Seattle: 1,926 nonstop flights a year

On time (12 months)

76%

Cancelled

1.0%

avg delay 16 min

Best time to leave

Noon to 3 PM

93% on time vs 59% 6 to 9 PM

Most reliable airline

United

78% chance on time

Check IAD to SEA fares

Lowest nonstop fare seen in the next two months: $215 (Alaska 409 on 2026-11-26). Fares open on our travel partner (Aviasales). Pick the flight number you chose here.

Most reliable nonstop flights

Ranked by the chance the flight operates and arrives within 15 minutes of schedule, from Jun 2025 to May 2026 records.

  1. #1 · United 2241

    1:15 PM → 4:00 PM5h 45m nonstop

    Local times, typical schedule. Last flown 2026-05-31.

    90%

    chance on time

    On time (history)
    100%
    Cancelled
    0.0%
    Avg arrival delay
    0 min
    • Arrived on time 100% of the time (11 flights, Jun 2025 to May 2026).
    • Leaves in this route's most on-time window (Noon to 3 PM: 93% on time; 6 to 9 PM: 59%).
    • Departs inside IAD's trouble window: 75% of its 63 ground stops and delay programs started between 1 PM and 7 PM.
    • Lands inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.

    Limited track record · 11 flights

    Find United 2241 fares Opens this date on Aviasales

  2. #2 · United 2101

    9:00 AM → 11:48 AM5h 48m nonstop

    Local times, typical schedule. Last flown 2026-05-31.

    82%

    chance on time

    On time (history)
    90%
    Cancelled
    0.0%
    Avg arrival delay
    5 min
    • Arrived on time 90% of the time (29 flights, Jun 2025 to May 2026).
    • Departs outside IAD's trouble window (1 PM to 7 PM, when 75% of its 63 ground stops and delay programs started).
    • Short track record (29 flights), so its score leans on the airline's record at this hour.

    Limited track record · 29 flights

    Find United 2101 fares Opens this date on Aviasales

  3. #3 · United 788

    1:01 PM → 3:42 PM5h 41m nonstop

    Local times, typical schedule. Last flown 2026-05-18.

    81%

    chance on time

    On time (history)
    73%
    Cancelled
    0.0%
    Avg arrival delay
    17 min
    • Arrived on time 73% of the time (15 flights, Jun 2025 to May 2026).
    • Leaves in this route's most on-time window (Noon to 3 PM: 93% on time; 6 to 9 PM: 59%).
    • Departs inside IAD's trouble window: 75% of its 63 ground stops and delay programs started between 1 PM and 7 PM.
    • 55% of its delay minutes came from the plane arriving late from an earlier flight.

    Limited track record · 15 flights

    Find United 788 fares Opens this date on Aviasales

  4. #4 · Alaska 351

    7:00 AM → 9:53 AM5h 53m nonstop

    Local times, typical schedule. Last flown 2026-05-31.

    78%

    chance on time

    On time (history)
    79%
    Cancelled
    0.6%
    Avg arrival delay
    11 min
    • Arrived on time 79% of the time (324 flights, Jun 2025 to May 2026).
    • Departs outside IAD's trouble window (1 PM to 7 PM, when 75% of its 63 ground stops and delay programs started).

    Strong track record · 324 flights

    Find Alaska 351 fares Opens this date on Aviasales

  5. #5 · Alaska 375

    9:00 AM → 11:47 AM5h 47m nonstop

    Local times, typical schedule. Last flown 2026-05-31.

    77%

    chance on time

    On time (history)
    82%
    Cancelled
    1.1%
    Avg arrival delay
    11 min
    • Arrived on time 82% of the time (173 flights, Jun 2025 to May 2026).
    • Departs outside IAD's trouble window (1 PM to 7 PM, when 75% of its 63 ground stops and delay programs started).

    Moderate track record · 173 flights

    Find Alaska 375 fares Opens this date on Aviasales

  6. #6 · Delta 1015

    7:00 AM → 10:03 AM5h 54m nonstop

    Local times, typical schedule. Last flown 2026-05-31.

    77%

    chance on time

    On time (history)
    78%
    Cancelled
    1.4%
    Avg arrival delay
    23 min
    • Arrived on time 78% of the time (343 flights, Jun 2025 to May 2026).
    • Departs outside IAD's trouble window (1 PM to 7 PM, when 75% of its 63 ground stops and delay programs started).

    Strong track record · 343 flights

    Find Delta 1015 fares Opens this date on Aviasales

  7. #7 · United 326

    5:55 PM → 8:53 PM5h 58m nonstop

    Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as United 1303; its record covers all of them.

    72%

    chance on time

    On time (history)
    72%
    Cancelled
    0.0%
    Avg arrival delay
    19 min
    • Arrived on time 72% of the time (306 flights, Jun 2025 to May 2026).
    • Never cancelled in 309 scheduled flights.
    • Departs inside IAD's trouble window: 75% of its 63 ground stops and delay programs started between 1 PM and 7 PM.
    • Lands inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.

    Strong track record · 306 flights

    Find United 326 fares Opens this date on Aviasales

  8. #8 · Alaska 406

    6:27 PM → 9:35 PM6h 08m nonstop

    Local times, typical schedule. Last flown 2026-03-16.

    61%

    chance on time

    On time (history)
    62%
    Cancelled
    2.2%
    Avg arrival delay
    32 min
    • Arrived on time 62% of the time (133 flights, Jun 2025 to May 2026).
    • Leaves in this route's least on-time window (6 to 9 PM: 59% on time; Noon to 3 PM: 93%).
    • Departs inside IAD's trouble window: 75% of its 63 ground stops and delay programs started between 1 PM and 7 PM.
    • Lands inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.

    Moderate track record · 133 flights

    Find Alaska 406 fares Opens this date on Aviasales

  9. #9 · Alaska 737

    7:11 PM → 10:02 PM5h 51m nonstop

    Local times, typical schedule. Last flown 2026-05-31.

    55%

    chance on time

    On time (history)
    54%
    Cancelled
    0.0%
    Avg arrival delay
    23 min
    • Arrived on time 54% of the time (69 flights, Jun 2025 to May 2026).
    • Never cancelled in 69 scheduled flights.
    • Leaves in this route's least on-time window (6 to 9 PM: 59% on time; Noon to 3 PM: 93%).
    • Departs outside IAD's trouble window (1 PM to 7 PM, when 75% of its 63 ground stops and delay programs started).

    Moderate track record · 69 flights

    Find Alaska 737 fares Opens this date on Aviasales

Airlines on this route

Season-adjusted chance of operating and arriving on time.

  • United Airlines78%

    730 flights · 79% on time as flown · 0.6% cancel

  • Delta Air Lines76%

    361 flights · 77% on time as flown · 1.5% cancel

  • Alaska Airlines71%

    835 flights · 72% on time as flown · 1.1% cancel

On time by departure time

All airlines, scheduled local departure, Jun 2025 to May 2026.

  • Before 9 AM80%

    754 flights · avg delay 16 min

  • 9 AM to noon79%

    246 flights · avg delay 11 min

  • Noon to 3 PM93%

    165 flights · avg delay 7 min

  • 3 to 6 PM72%

    381 flights · avg delay 18 min

  • 6 to 9 PM59%

    303 flights · avg delay 25 min

  • After 9 PM70%

    77 flights · avg delay 15 min

Best day: Wednesday (82%). Worst: Monday (77%).

On time by month

All airlines, Jun 2023 to May 2026. Several years per month, so one stormy season doesn't define a month. Travel-month estimates use this seasonal pattern.

J
80
F
78
M
75
A
82
M
80
J
71
J
73
A
79
S
88
O
91
N
82
D
73

What delays this route

  • Airline (crew, maintenance, boarding)41%
  • Air traffic control and airport volume30%
  • Late-arriving aircraft19%
  • Severe weather10%

Share of delay minutes by the cause airlines report to the US DOT.

Historical odds, not a guarantee. Built from the US DOT Bureau of Transportation Statistics on-time reports (Jun 2025 to May 2026), FAA ground stop and delay program advisories, and 20 years of airport weather observations. Covers US airlines that report to the DOT; schedules are flights operated recently, so confirm times when you book. ATIS Alerts is not affiliated with any airline. Fares are what Aviasales travelers saw in recent searches (USD, one way, 1 adult), not live quotes; the partner site shows the current price. Fare links go to our travel partner and may earn us a commission at no cost to you. Affiliate disclosure

IAD to SEA questions

What time of day is best to fly IAD to SEA?
Noon to 3 PM: 93% of flights arrived on time, against 59% for departures 6 to 9 PM.
Which airline is most on time from IAD to SEA?
United, with a season-adjusted 78% chance of operating and arriving on time over 730 flights. The adjustment compares each airline with what the route did in the months it flew, so a carrier that skipped a stormy month gets no free credit.
What is the worst month for delays on IAD to SEA?
June (71% on time); the best was October (91%), averaged over Jun 2023 to May 2026.
Is this a prediction for my flight?
No. These are historical odds from the US DOT on-time reports, FAA advisories and airport weather records. Check your flight status and the FAA delay board on the day you fly.

More routes from IAD

Live status: FAA delays and ground stops