OnTimeStats

Historical on-time performance

San Juan to Boston

1,674 miData through May 2026Source: US DOT · BTS

Flights on SJU–BOS arrive on time 70% of the time over the last 12 months.

On-time rate70%arrived within 15 min
p90 delay60 min1 in 10 flights is worse (tail risk)
Cancelled2.7%of scheduled flights

based on 1,911 flights over the last 12 months. On-time means arriving within 15 minutes (BTS standard).

By airline

How each carrier compares

  • Delta Air Linesbest
    On-time77%
    Medianon time
    p9035 min
    Cancel1.5%
    Flights398
  • Spirit Airlines
    On-time71%
    Medianon time
    p9060 min
    Cancel3.9%
    Flights76
  • JetBlue Airways
    On-time68%
    Medianon time
    p9070 min
    Cancel2.9%
    Flights1,437

Why flights run late

Delay causes

  • Airline33%
  • Weather1%
  • Air traffic (NAS)18%
  • Late aircraft47%
  • Security0%

Most delay minutes here are attributed to Late aircraft.

When flights don't go

Why flights were cancelled

  • Airline22%
  • Weather45%
  • Air traffic (NAS)29%
  • Security4%

Most cancellations here are attributed to Weather. Shares are among 51 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 SJU → BOS

All airlines · rolling 36 months (2023-06 .. 2026-05).

Best time of day

On-time rates are fairly even by time of day on this route — ranging from 58% to 81% on time.

  • Early mornings81% on time · p90 45 min · 279 flights
  • Mornings77% on time · p90 35 min · 1,616 flights
  • Middays76% on time · p90 50 min · 1,863 flights
  • Afternoons67% on time · p90 80 min · 1,325 flights
  • Overnights61% on time · p90 95 min · 441 flights
  • Evenings58% on time · p90 100 min · 792 flights

Best day of week

On-time rates are fairly even by day on this route — ranging from 67% to 74% on time.

  • Wednesdays74% on time · p90 50 min · 822 flights
  • Tuesdays73% on time · p90 55 min · 847 flights
  • Mondays72% on time · p90 65 min · 888 flights
  • Fridays72% on time · p90 60 min · 891 flights
  • Thursdays70% on time · p90 65 min · 926 flights
  • Sundays70% on time · p90 70 min · 927 flights
  • Saturdays67% on time · p90 75 min · 1,015 flights

Keep exploring

Related pages

Methodology

A flight is on time when it arrives within 15 minutes of schedule — the US DOT / BTS standard. Median and p90(the “1-in-10 bad day”) are read from the full arrival-delay distribution, never averaged across periods.

Figures cover a carrier’s own BTS-coded flights. Cells below ~200 flights are flagged as limited data. All numbers are pre-computed from public BTS On-Time Performance data.