Flight number record
B6 561
JetBlue Airways · Boston to San Juan
- Route
- BOS → SJU
- Departs
- 18:45
- Flights
- 274
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s B6 561, check with JetBlue Airways.
B6 561 earns an F−, which is as low as this site's scale goes for a reason. Only 48.5% of flights arrive inside the 15-minute window, 29 points worse than the national rate of 77.3%. Late arrivals average a little over an hour. Treat any tight connection here as a coin flip. That rests on 274 flights, with a median arrival 17 minutes late.
The national on-time rate over the same period is 77.3%, so B6 561 runs 29 points behind the country as a whole. Across a thousand flights that is about 288 extra late arrivals.
Key figures
On time
48.5%
Arrivals under 15 minutes late, of 264 completed flights
Avg delay
76 min
Across delayed arrivals only, not all flights
Cancelled
3.65%
National rate is 1.89%
1 hour+ late
21.6%
National rate is 8.3%
These figures cover 274 flights between September 2025 and August 2026. Beyond the headline rate, 21.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When B6 561 flies
B6 561 flies BOS to SJU without a single fixed slot. Its most common scheduled departure was 18:45, used on 30 of 274 flights.
- Departs 18:4530 flights10.9%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 18:45 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and B6 561 runs 20 points worse at 48.5%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
B6 561 next to BOS to SJU
Every carrier on BOS to SJU combined arrived on time 66.8% of the time across 1,717 flights, so B6 561 is 18 points behind it. JetBlue flew 1,142 flights on the same city pair under all its flight numbers, including this one, and those ran 66.5% on time. Across its whole network JetBlue Airways managed 71.3%, which this flight trails by 23 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| B6 561thin sample | 274 | 48.5% | 76 min | 3.65% | F− |
| All JetBlue Airways on BOS–SJU | 1,142 | 66.5% | 73 min | 2.80% | C |
| All carriers on BOS–SJU | 1,717 | 66.8% | 76 min | 2.97% | C |
| JetBlue Airways, whole network | 240,615 | 71.3% | 77 min | 3.56% | C− |
Across the year
B6 561 quarter by quarter
B6 561 did not run the same all year. Its best quarter was Apr–Jun 2026 at 55.7% on time and its weakest Jul–Sep 2026 at 29.8%, a swing of 26 points on roughly 69 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 20252 flights—
- Oct–Dec 202555 flights50.9%
- Jan–Mar 202685 flights52.5%
- Apr–Jun 202670 flights55.7%
- Jul–Sep 202662 flights29.8%
Scale runs 20% to 60%. Rows with fewer than 30 flights show a dash.
By weekday, B6 561 did best on Tuesday at 58.3% on time and worst on Sunday at 35.0%. Each day rests on about 39 flights, so a gap of 23 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late B6 561 runs when it is late
The 136 late arrivals split 23 under half an hour, 56 between 30 and 60 minutes, and 57 an hour or more.
- 15+ min early31 flights11.7%
- Within 15 min97 flights36.7%
- 15–29 min late23 flights8.7%
- 30–59 min late56 flights21.2%
- 1–2 hours late33 flights12.5%
- 2+ hours late24 flights9.1%
Scale runs 0% to 100%.
Share of 264 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 132 departures that left 15 minutes late or more, only 12 made it up before arrival. In the other direction, 16 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SJU.
The worst days
Worst days for B6 561
The latest arrival of the period was on 7 July 2026, 5 hours 11 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 7 July 2026 | 5 hours 11 minutes | Carrier |
| 20 February 2026 | 5 hours 7 minutes | Carrier |
| 26 January 2026 | 4 hours 58 minutes | Extreme weather |
| 7 February 2026 | 4 hours 9 minutes | Late-arriving aircraft |
| 14 December 2025 | 4 hours 4 minutes | Carrier |
Delay causes
Why B6 561 runs late
Late-arriving aircraft accounts for 46% of the 10,000 delay minutes carriers reported here, and the remaining four split what is left.
- 46%Late-arriving aircraft
- 34%Carrier
- 18%National Airspace System
- 3%Extreme weather
46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 10,000 reported delay minutes here, that single category outweighs weather by 16 to one. The split is drawn from 10,341 delay minutes reported on B6 561.
Cancellations run at 3.65%, against 1.89% nationally. That is roughly one flight in 25 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and routes
What a delay on this flight costs
21.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
At 1,674 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
Every one of the 274 flights under B6 561 in the data flew BOS to SJU. The number was not reused on any other city pair, which makes this a clean record of one route.
One caution: this is a thin sample. 274 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking B6 561
For a booking, the cancellation rate is the figure to plan around on B6 561: 3.65% of its 274 scheduled flights did not operate. A late arrival costs a little over an hour, but a cancellation costs the day, so leave a later option open.
Related
Where to go next
- BOS to SJU, every carrier and departure
- SJU to BOS, the return direction
- Delta Air Lines 1780 on the same route76.5%
- JetBlue Airways 861 on the same route73.4%
- Boston Logan International (BOS) delay statistics
- Luis Munoz Marin International (SJU) delay statistics
- JetBlue Airways on-time record
- Every JetBlue Airways flight number with a record
- The most and least reliable flight numbers in the US
- Why the first flight of the morning is statistically safest
A flight number here means JetBlue Airways’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.