Historical on-time performance
Washington to San Juan
1,571 miData through May 2026Source: US DOT · BTS
Flights on IAD–SJU arrive on time 80% of the time over the last 12 months.
On-time rate80%arrived within 15 min
p90 delay35 min1 in 10 flights is worse (tail risk)
Cancelled0.5%of scheduled flights
based on 575 flights over the last 12 months. On-time means arriving within 15 minutes (BTS standard).
By airline
How each carrier compares
- United AirlinesOn-time80%Medianon timep9035 minCancel0.5%Flights575
Why flights run late
Delay causes
- Airline26%
- Weather14%
- Air traffic (NAS)50%
- Late aircraft10%
- Security0%
Most delay minutes here are attributed to Air traffic (NAS).
When flights don't go
Why flights were cancelled
- Airline0%
- Weather67%
- Air traffic (NAS)33%
- Security0%
Most cancellations here are attributed to Weather. 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 → SJU
All airlines · rolling 36 months (2023-06 .. 2026-05).
Best time of day
Mornings are the most reliable time of day to fly this route — 88% on time.
- Mornings88% on time · p90 15 min · 1,043 flights
- Evenings72% on time · p90 45 min · 444 flights
Best day of week
On-time rates are fairly even by day on this route — ranging from 76% to 87% on time.
- Wednesdays87% on time · p90 15 min · 191 flights · limited
- Fridays86% on time · p90 20 min · 208 flights
- Tuesdays80% on time · p90 30 min · 205 flights
- Thursdays80% on time · p90 30 min · 221 flights
- Mondays80% on time · p90 40 min · 206 flights
- Saturdays77% on time · p90 35 min · 282 flights
- Sundays76% on time · p90 55 min · 286 flights
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