Historical on-time performance
Washington to Seattle
2,306 miData through Dec 2025Source: US DOT · BTS
Flights on IAD–SEA arrive on time 77% of the time over the last 12 months.
On-time rate77%arrived within 15 min
p90 delay40 min1 in 10 flights is worse (tail risk)
Cancelled0.6%of scheduled flights
based on 1,871 flights over the last 12 months. On-time means arriving within 15 minutes (BTS standard).
By airline
How each carrier compares
- Alaska AirlinesOn-time73%Medianon timep9050 minCancel0.8%Flights832
- United AirlinesOn-time79%Medianon timep9035 minCancel0.5%Flights733
- Delta Air LinesbestOn-time86%Medianon timep9020 minCancel0.3%Flights306
Why flights run late
Delay causes
- Airline38%
- Weather12%
- Air traffic (NAS)26%
- Late aircraft24%
- Security1%
Most delay minutes here are attributed to Airline.
Over time
On-time trend
By season
On-time rate by month
When to fly
Best time to fly IAD → SEA
All airlines · rolling 36 months (2023-01 .. 2025-12).
Best time of day
Middays are the most reliable time of day to fly this route — 92% on time.
- Middays92% on time · p90 5 min · 436 flights
- Mornings85% on time · p90 20 min · 2,719 flights
- Afternoons81% on time · p90 25 min · 167 flights · limited
- Evenings73% on time · p90 50 min · 2,861 flights
- Overnights69% on time · p90 50 min · 268 flights
Best day of week
On-time rates are fairly even by day on this route — ranging from 77% to 83% on time.
- Tuesdays83% on time · p90 25 min · 893 flights
- Wednesdays81% on time · p90 30 min · 902 flights
- Fridays79% on time · p90 40 min · 951 flights
- Thursdays79% on time · p90 35 min · 941 flights
- Saturdays78% on time · p90 30 min · 872 flights
- Mondays78% on time · p90 35 min · 951 flights
- Sundays77% on time · p90 40 min · 941 flights
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