Historical on-time performance
Boston to San Juan
1,674 miData through May 2026Source: US DOT · BTS
Flights on BOS–SJU arrive on time 69% of the time over the last 12 months.
On-time rate69%arrived within 15 min
p90 delay65 min1 in 10 flights is worse (tail risk)
Cancelled2.5%of scheduled flights
based on 1,734 flights over the last 12 months. On-time means arriving within 15 minutes (BTS standard).
By airline
How each carrier compares
- Delta Air LinesbestOn-time75%Medianon timep9035 minCancel1.5%Flights398
- JetBlue AirwaysOn-time68%Medianon timep9070 minCancel2.4%Flights1,260
- Spirit AirlinesOn-time43%Median15 minp90155 minCancel9.2%Flights76
Why flights run late
Delay causes
- Airline31%
- Weather3%
- Air traffic (NAS)33%
- Late aircraft32%
- Security0%
Most delay minutes here are attributed to Air traffic (NAS).
When flights don't go
Why flights were cancelled
- Airline26%
- Weather42%
- Air traffic (NAS)28%
- Security5%
Most cancellations here are attributed to Weather. Shares are among 43 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 BOS → 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 — 76% on time.
- Mornings76% on time · p90 40 min · 2,239 flights
- Evenings61% on time · p90 90 min · 572 flights
- Middays60% on time · p90 85 min · 1,756 flights
- Afternoons59% on time · p90 105 min · 592 flights
- Overnights57% on time · p90 90 min · 746 flights
Best day of week
On-time rates are fairly even by day on this route — ranging from 62% to 68% on time.
- Fridays68% on time · p90 80 min · 858 flights
- Wednesdays68% on time · p90 60 min · 772 flights
- Tuesdays67% on time · p90 65 min · 794 flights
- Saturdays67% on time · p90 60 min · 863 flights
- Thursdays65% on time · p90 70 min · 878 flights
- Mondays64% on time · p90 85 min · 861 flights
- Sundays62% on time · p90 85 min · 879 flights
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