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Route on-time record

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

Seattle (Seattle–Tacoma International Airport) to Dulles (Washington Dulles International Airport). 1,928 nonstop flights in Jun 2025 to May 2026, 81% arrived within 15 minutes and 0.7% were cancelled. The most reliable flight number was United 688 at 8:00 AM.

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

SEA → IAD

Seattle to Dulles: 1,928 nonstop flights a year

On time (12 months)

81%

Cancelled

0.7%

avg delay 12 min

Best time to leave

Before 9 AM

90% on time vs 76% 3 to 6 PM

Most reliable airline

United

85% chance on time

Check SEA to IAD fares

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 688

    8:00 AM → 4:09 PM5h 09m nonstop

    Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as United 2861, 2474; its record covers all of them.

    93%

    chance on time

    On time (history)
    95%
    Cancelled
    0.0%
    Avg arrival delay
    2 min
    • Arrived on time 95% of the time (65 flights, Jun 2025 to May 2026).
    • Never cancelled in 66 scheduled flights.
    • Leaves in this route's most on-time window (Before 9 AM: 90% on time; 3 to 6 PM: 76%).
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).

    Moderate track record · 65 flights

    Find United 688 fares Opens this date on Aviasales

  2. #2 · United 2131

    1:00 PM → 9:06 PM5h 06m nonstop

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

    91%

    chance on time

    On time (history)
    97%
    Cancelled
    0.0%
    Avg arrival delay
    1 min
    • Arrived on time 97% of the time (34 flights, Jun 2025 to May 2026).
    • Never cancelled in 34 scheduled flights.
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
    • Short track record (34 flights), so its score leans on the airline's record at this hour.

    Limited track record · 34 flights

    Find United 2131 fares Opens this date on Aviasales

  3. #3 · United 755

    1:07 PM → 9:16 PM5h 09m nonstop

    Local times, typical schedule. Last flown 2026-05-20.

    85%

    chance on time

    On time (history)
    85%
    Cancelled
    0.0%
    Avg arrival delay
    9 min
    • Arrived on time 85% of the time (20 flights, Jun 2025 to May 2026).
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
    • Short track record (20 flights), so its score leans on the airline's record at this hour.

    Limited track record · 20 flights

    Find United 755 fares Opens this date on Aviasales

  4. #4 · United 2851

    8:10 AM → 4:22 PM5h 12m nonstop

    Local times, typical schedule. Last flown 2026-05-20.

    84%

    chance on time

    On time (history)
    76%
    Cancelled
    0.0%
    Avg arrival delay
    11 min
    • Arrived on time 76% of the time (21 flights, Jun 2025 to May 2026).
    • Leaves in this route's most on-time window (Before 9 AM: 90% on time; 3 to 6 PM: 76%).
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
    • Lands inside IAD's trouble window: 75% of its 63 ground stops and delay programs started between 1 PM and 7 PM.

    Limited track record · 21 flights

    Find United 2851 fares Opens this date on Aviasales

  5. #5 · United 264

    10:41 PM → 6:50 AM5h 09m nonstop

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

    84%

    chance on time

    On time (history)
    86%
    Cancelled
    0.0%
    Avg arrival delay
    7 min
    • Arrived on time 86% of the time (22 flights, Jun 2025 to May 2026).
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
    • Short track record (22 flights), so its score leans on the airline's record at this hour.

    Limited track record · 22 flights

    Find United 264 fares Opens this date on Aviasales

  6. #6 · Alaska 367

    9:40 PM → 5:40 AM5h 00m nonstop

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

    82%

    chance on time

    On time (history)
    83%
    Cancelled
    0.4%
    Avg arrival delay
    9 min
    • Arrived on time 83% of the time (270 flights, Jun 2025 to May 2026).
    • Departs inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.

    Strong track record · 270 flights

    Find Alaska 367 fares Opens this date on Aviasales

  7. #7 · Alaska 737

    10:09 AM → 6:11 PM5h 02m nonstop

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

    80%

    chance on time

    On time (history)
    83%
    Cancelled
    0.7%
    Avg arrival delay
    8 min
    • Arrived on time 83% of the time (143 flights, Jun 2025 to May 2026).
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
    • Lands inside IAD's trouble window: 75% of its 63 ground stops and delay programs started between 1 PM and 7 PM.

    Moderate track record · 143 flights

    Find Alaska 737 fares Opens this date on Aviasales

  8. #8 · Delta 541

    3:55 PM → 11:49 PM4h 56m nonstop

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

    75%

    chance on time

    On time (history)
    77%
    Cancelled
    1.4%
    Avg arrival delay
    19 min
    • Arrived on time 77% of the time (343 flights, Jun 2025 to May 2026).
    • Leaves in this route's least on-time window (3 to 6 PM: 76% on time; Before 9 AM: 90%).
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).

    Strong track record · 343 flights

    Find Delta 541 fares Opens this date on Aviasales

  9. #9 · Alaska 348

    3:55 PM → 12:09 AM5h 14m nonstop

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

    72%

    chance on time

    On time (history)
    72%
    Cancelled
    0.6%
    Avg arrival delay
    12 min
    • Arrived on time 72% of the time (172 flights, Jun 2025 to May 2026).
    • Leaves in this route's least on-time window (3 to 6 PM: 76% on time; Before 9 AM: 90%).
    • Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
    • 54% of its delay minutes came from the plane arriving late from an earlier flight.

    Moderate track record · 172 flights

    Find Alaska 348 fares Opens this date on Aviasales

Airlines on this route

Season-adjusted chance of operating and arriving on time.

  • United Airlines85%

    732 flights · 85% on time as flown · 0.6% cancel

  • Alaska Airlines79%

    835 flights · 79% on time as flown · 0.5% cancel

  • Delta Air Lines76%

    361 flights · 77% on time as flown · 1.2% cancel

On time by departure time

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

  • Before 9 AM90%

    458 flights · avg delay 8 min

  • 9 AM to noon79%

    268 flights · avg delay 10 min

  • Noon to 3 PM85%

    134 flights · avg delay 9 min

  • 3 to 6 PM76%

    420 flights · avg delay 17 min

  • After 9 PM78%

    648 flights · avg delay 14 min

Best day: Wednesday (85%). Worst: Sunday (78%).

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
79
F
84
M
80
A
84
M
79
J
76
J
75
A
80
S
83
O
88
N
84
D
83

What delays this route

  • Airline (crew, maintenance, boarding)45%
  • Late-arriving aircraft38%
  • Air traffic control and airport volume14%
  • Severe weather3%

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

Finding the most reliable connections from SEA to IAD…

SEA to IAD questions

What time of day is best to fly SEA to IAD?
Before 9 AM: 90% of flights arrived on time, against 76% for departures 3 to 6 PM. Later flights inherit delays from earlier ones, so the first departures of the day usually run best.
Which airline is most on time from SEA to IAD?
United, with a season-adjusted 85% chance of operating and arriving on time over 732 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 SEA to IAD?
July (75% on time); the best was October (88%), 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 SEA

Live status: FAA delays and ground stops