Route profile
SJU→BOS
Flight reliability, delays and best times to fly from San Juan to Boston, 1,674 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 14% of comparable major US routes (4,598 compared)
Calculated from 6,425 flights. How this is calculated · What counts as on time
SJU → BOS arrives on time 73.0% of the time; the return trip, BOS → SJU, arrives on time 67.7% of the time, a 5.3-point gap between the two directions of the same city pair.
SJU → BOS spends 24.5 minutes on the ground on a 1,674-mile trip: 14.5 minutes from pushback to wheels-up at SJU and 10.0 minutes from touchdown to gate at BOS.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What sets this route apart
Where SJU to BOS differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
SJU to BOS struggles most at 6 PM: 55.8% of its flights scheduled then arrive on time, 14.1 points behind the 69.9% on routes of similar length at the same hour. Against all other routes the gap is 12.8 points.
SJU to BOS is at its best against routes of similar length for flights scheduled at 1 PM: 80.1% arrive on time, 5.2 points ahead of the 74.9% those routes manage at that hour. Against all other routes the gap is 3 points.
Saturday is the day SJU to BOS slips furthest against routes of similar length, 70.2% on time where they average 78.8%, 8.6 points lower. Against all other routes the gap is 8.9 points.
In August, SJU to BOS runs 13 points below routes of similar length, 62.8% on time to 75.8%. Against all other routes the gap is 13.7 points.
June is kinder to SJU to BOS than to routes of similar length: 77.4% on time against 71.8%, 5.6 points better. Against all other routes the gap is 4.7 points.
SJU to BOS against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 6 PM departures | 55.8% | routes of similar length | 69.9% | −14.1 pts | 242 here, 89,463 there |
| Hour: 1 PM departures | 80.1% | routes of similar length | 74.9% | +5.2 pts | 1,098 here, 83,303 there |
| Weekday: Saturday | 70.2% | routes of similar length | 78.8% | −8.6 pts | 1,002 here, 199,209 there |
| Month: August | 62.8% | routes of similar length | 75.8% | −13.0 pts | 580 here, 127,842 there |
| Month: June | 77.4% | routes of similar length | 71.8% | +5.6 pts | 513 here, 130,743 there |
Each comparison pools the flights of other routes, with this route’s own left out. Similar length means within 15% of this route’s 1,674 miles, with at least 5 such routes. A bucket is set against the most comparable group that has enough flights: similar length, then the same origin (at least 3 routes), then all other routes. Hours, weekdays and months appear only where both sides have 120 completed flights, and airlines where both have 600. The gap must be at least 2 points and 2 standard errors, and only the largest gap each way is kept per measure. These are differences in the flights counted, not causes.
Why SJU → BOS flights are cancelled
July 2023 – July 2026
SJU → BOS cancelled 114 of 6,425 scheduled flights — about 1 in every 56. The reason filed most often was extreme weather, 37.7% of the cancellations coded on this route — about 1 in every 149 scheduled flights.
Share of cancellations
Of 114 cancelled departures carrying a reason code.
What each reason means
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
43 cancellations, 37.7% of the total.
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
38 cancellations, 33.3% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
31 cancellations, 27.2% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
2 cancellations, 1.8% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
114 coded cancellations were recorded on SJU → BOS; the section appears from 50.
When it goes wrong
July 2023 – July 2026
64 min late
against a median of 5 min early
SJU → BOS has an average that understates its risk: a typical arrival is 5 min early, but the worst tenth are 69 minutes worse than that. If the trip has something unmissable at the end of it, the median is the wrong number to plan against.
Percentiles over 6,425 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at BOS after arriving from SJU.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 41% | Likely to miss |
| 45 min | 26% | High risk |
| 60 min | 18% | High risk |
| 90 min | 10% | Some risk |
| 120 min | 7.0% | Some risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.77% of the time and diverts 0.39% of the time, which a late arrival never shows up in.
Chance of missing is the share of 6,286 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 64 minutes late (90th-percentile gate arrival delay), over 6,425 operations.
Any other layover length: connection checker.
Best time to fly
SJU → BOS flights departing 5–9 AM arrived on time 79.6% of the time, against 61.8% for 6–9 PM departures, a gap of 17.8 percentage points.
By departure window
By departure hour
- 12 AM to 4 AM: too few flights to score
- 5 AM: 82.8% on time from 534 flights
- 6 AM: 77.2% on time from 664 flights
- 7 AM: 78.9% on time from 182 flights
- 8 AM: 79.9% on time from 211 flights
- 9 AM: too few flights to score
- 10 AM: 81.8% on time from 184 flights
- 11 AM: 68.6% on time from 159 flights
- 12 PM: 68.8% on time from 352 flights
- 1 PM: 80.1% on time from 1,116 flights
- 2 PM: 76.5% on time from 657 flights
- 3 PM: 61.0% on time from 544 flights
- 4 PM: 68.9% on time from 210 flights
- 5 PM: 59.7% on time from 203 flights
- 6 PM: 55.8% on time from 249 flights
- 7 PM: 62.6% on time from 344 flights
- 8 PM: 66.4% on time from 275 flights
- 9 PM to 11 PM: too few flights to score
Why SJU → BOS runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for SJU → BOS. Only delays of 15 minutes or more are attributed. What the five causes mean
Late-arriving aircraft is the largest cause on SJU → BOS, at 42.7%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 79.6% of the time and 6–9 PM departures 61.8%.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| JetBlue | 4,294 | 69.6% | 1.91% | -3 min | 12.8% |
| Delta Air Lines | 1,207 | 83.2% | 0.91% | -11 min | 5.4% |
| Spirit Airlines | 683 | 76.8% | 2.49% | -8 min | 7.7% |
| Frontier Airlines | 241 | 71.3% | 1.66% | -3 min | 6.3% |
JetBlue flew 66.8% of the 6,425 flights listed. Spirit Airlines cancelled 2.49% of its flights here against 0.91% for Delta Air Lines.
Delta Air Lines arrived on time 13.6 percentage points more often than JetBlue on this route.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
| Flight | Scheduled | Operations | On time |
|---|---|---|---|
| B6562 JetBlue | 6:00 AM | 804 | 78.0% |
Weekly and seasonal patterns
By day of week
Wednesday is historically the most reliable day and Saturday the least, a gap of 4.9 percentage points.
By month
- Jan: 71.1%
- Feb: 71.1%
- Mar: 75.4%
- Apr: 76.5%
- May: 79.1%
- Jun: 77.4%
- Jul: 69.4%
- Aug: 62.8%
- Sep: 75.9%
- Oct: 75.3%
- Nov: 75.5%
- Dec: 70.7%
August is historically the weakest month and May the strongest, a spread of 16.3 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 58.3% from 181 flights
- August 2023: 51.4% from 181 flights
- September 2023: too few flights to score (119)
- October 2023: 77.6% from 148 flights
- November 2023: 79.1% from 160 flights
- December 2023: 73.4% from 173 flights
- January 2024: 77.8% from 168 flights
- February 2024: 69.8% from 164 flights
- March 2024: 73.7% from 174 flights
- April 2024: 78.5% from 180 flights
- May 2024: 78.1% from 171 flights
- June 2024: 70.2% from 221 flights
- July 2024: 76.9% from 239 flights
- August 2024: 68.9% from 230 flights
- September 2024: too few flights to score (119)
- October 2024: 73.6% from 122 flights
- November 2024: 71.2% from 163 flights
- December 2024: 71.2% from 208 flights
- January 2025: 72.4% from 197 flights
- February 2025: 77.0% from 203 flights
- March 2025: 76.8% from 232 flights
- April 2025: 81.7% from 213 flights
- May 2025: 77.6% from 156 flights
- June 2025: 85.3% from 163 flights
- July 2025: 74.7% from 179 flights
- August 2025: 66.3% from 186 flights
- September 2025: too few flights to score (84)
- October 2025: too few flights to score (98)
- November 2025: 76.7% from 120 flights
- December 2025: 67.6% from 189 flights
- January 2026: 63.6% from 207 flights
- February 2026: 66.1% from 207 flights
- March 2026: 75.3% from 235 flights
- April 2026: 69.8% from 215 flights
- May 2026: 82.1% from 145 flights
- June 2026: 79.3% from 136 flights
- July 2026: 63.8% from 139 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 70.9% against 75.3% in the 12 months before — declining by 4.4 percentage points.
Data and methodology
Calculated by FlyerIntel from 6,425 SJU → BOS flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed