Historical on-time performance
Washington to St. Thomas
1,606 miData through May 2026Source: US DOT · BTS
Flights on IAD–STT arrive on time 87% of the time over the last 12 months.
On-time rate87%arrived within 15 min
p90 delay15 min1 in 10 flights is worse (tail risk)
Cancelled1.1%of scheduled flights
based on 266 flights over the last 12 months. On-time means arriving within 15 minutes (BTS standard).
By airline
How each carrier compares
- United AirlinesOn-time87%Medianon timep9015 minCancel1.1%Flights266
Why flights run late
Delay causes
- Airline30%
- Weather1%
- Air traffic (NAS)48%
- Late aircraft21%
- Security0%
Most delay minutes here are attributed to Air traffic (NAS).
When flights don't go
Why flights were cancelled
- Airline0%
- Weather33%
- Air traffic (NAS)67%
- Security0%
Most cancellations here are attributed to Air traffic (NAS). Shares are among 3 cancellations with a reported cause (BTS reports causes from June 2003).
Over time
On-time trend
By season
On-time rate by month
When to fly
Best time to fly IAD → STT
All airlines · rolling 36 months (2023-06 .. 2026-05).
Best day of week
On-time rates are fairly even by day on this route — ranging from 85% to 92% on time.
- Thursdays92% on time · p90 10 min · 128 flights · limited
- Fridays88% on time · p90 15 min · 129 flights · limited
- Tuesdays87% on time · p90 15 min · 127 flights · limited
- Wednesdays87% on time · p90 20 min · 127 flights · limited
- Mondays86% on time · p90 25 min · 129 flights · limited
- Saturdays85% on time · p90 20 min · 172 flights · limited
- Sundays85% on time · p90 15 min · 135 flights · limited
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