Route profile
SJU→BOS
Flight reliability, delays and best times to fly from San Juan to Boston. · 1,674 miles
Right now
Current conditions at both ends of this route.
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Airport conditions describe the airfield, not any individual flight. An airport operating normally is not a guarantee that a specific flight will depart on time.
Route reliability
July 2023 – June 2026
Better than 14% of comparable major US routes (4,577 compared)
Calculated from 6,286 flights. How this is calculated
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – June 2026
Best time to fly
On-time arrival rate by scheduled local departure time.
SJU → BOS flights departing 5–9 AM arrived on time 79.9% of the time, against 62.5% for 6–9 PM departures — a gap of 17.4 percentage points.
By departure window
By departure hour
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Buckets with fewer than 120 flights are not scored.
Airlines on this route
Performance by the carrier that actually operated the flight.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| JetBlue | 4,186 | 69.9% | 1.70% | -3 min | 12.8% |
| Delta Air Lines | 1,176 | 83.1% | 0.94% | -11 min | 5.5% |
| Spirit Airlines | 683 | 76.8% | 2.49% | -8 min | 7.7% |
| Frontier Airlines | 241 | 71.3% | 1.66% | -3 min | 6.3% |
Delta Air Lines arrived on time 13.2 percentage points more often than JetBlue on this route.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Carriers with fewer than 200 flights on this route are not listed.
Individual flights on this route
The same route is not equally reliable at every hour. These are the flight numbers with enough operating history to judge separately.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Flight numbers with fewer than 270 operations on this route, or no longer scheduled, are not listed.
Weekly and seasonal patterns
By day of week
Wednesday is historically the most reliable day and Saturday the least, a gap of 5.1 percentage points.
By month
August is historically the weakest month and May the strongest, a spread of 16.4 percentage points.
Historical trend
On-time arrival rate by month.
Over the most recent 12 months (2025-07 to 2026-06), on-time arrivals averaged 71.7% against 75.5% in the 12 months before — declining by 3.8 percentage points.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026
Data and methodology
All figures on this page are calculated by FlyerIntel from 6,286 SJU → BOS flight records published by the US DOT Bureau of Transportation Statistics, covering July 2023 – June 2026. A flight is counted as delayed when it arrives 15 or more minutes after its scheduled arrival time, following BTS methodology. Cancelled and diverted flights have no arrival time and are excluded from on-time rates rather than counted as late.