Carrier route record
NKSJU→BOS
Spirit Airlines · San Juan to Boston
- Flights
- 142
- Period
- September 2025 to August 2026
- Share of route
- 7%
- Carriers
- 4
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Spirit Airlines.
Spirit on SJU to BOS sits in the middle of the pack with a C−. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 142 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 398 at 77.4% on time.
The national on-time rate over the same period is 77.3%, so Spirit on SJU to BOS runs 4 points behind the country as a whole. Across a thousand flights that is about 40 extra late arrivals.
Key figures
On time
73.3%
Arrivals under 15 minutes late, of 135 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
4.23%
National rate is 1.89%
Whole route
70.8%
Every carrier on SJU to BOS, 1,916 flights
These figures cover 142 flights between September 2025 and August 2026. Beyond the headline rate, 11.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Spirit against every carrier on SJU to BOS
Spirit flew 142 of the 1,916 flights on SJU to BOS, about 7% of it. Its 73.3% on time is 3 points better than the route as a whole, which runs 70.8%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from Delta at 77.4% to JetBlue at 68.5%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 77.4% of the time; JetBlue Airways manages 68.5%. Sample sizes sit next to every figure, because a two-point gap across 1,342 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 398 | 77.4% | 69 min | 1.51% | B |
| Spirit Airlines (this page)thin sample | 142 | 73.3% | 59 min | 4.23% | C− |
| Frontier Airlinesthin sample | 34 | 69.7% | 45 min | 2.94% | C |
| JetBlue Airways | 1,342 | 68.5% | 77 min | 3.58% | C− |
JetBlue Airways cancels 3.6% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Departure window
When Spirit runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 30 points, against 9 points between the best and worst carrier.
- 5am–8am—
- 8am–11am51 flights78.0%
- 11am–2pm53 flights82.4%
- 2pm–5pm38 flights52.9%
- 5pm–8pm—
- 8pm–5am—
Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 11am–2pm slot at 82.4% on time, ahead of 2pm–5pm at 52.9%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 11am–2pm window is the busiest, with 53 flights scheduled in it.
Across the year
Spirit on SJU to BOS through the year
- Oct–Dec 202514 flights—
- Jan–Mar 2026101 flights75.8%
- Apr–Jun 202627 flights—
Scale runs 65% to 80%. Rows with fewer than 30 flights show a dash.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 73.3% on time across 142 flights.
Split by quarter, Spirit on SJU to BOS logged 14 flights in Oct–Dec 2025, 101 flights in Jan–Mar 2026 and 27 flights in Apr–Jun 2026. Fewer than three of those quarters carried the 30 completed flights this site needs before printing a rate, so the 73.3% annual figure is the one to use.
Arrival by arrival
How late Spirit on SJU to BOS runs when it is late
Spirit on SJU to BOS often beats the schedule: 52 of 135 completed flights, 39%, arrived 15 minutes or more early. The 36 late arrivals split 11 under half an hour, 9 between 30 and 60 minutes, and 16 an hour or more.
- 15+ min early52 flights38.5%
- Within 15 min47 flights34.8%
- 15–29 min late11 flights8.1%
- 30–59 min late9 flights6.7%
- 1–2 hours late12 flights8.9%
- 2+ hours late4 flights3.0%
Scale runs 0% to 100%.
Share of 135 completed flights by arrival against schedule.
9 of 31 late departures made up the time and arrived on time, 29% of them. In the other direction, 14 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 BOS.
The worst days
Worst days for Spirit on SJU to BOS
The latest arrival of the period was on 13 February 2026, 2 hours 52 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The five worst days are spread across February, January, December and March, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 13 February 2026 | 2 hours 52 minutes | Late-arriving aircraft |
| 4 January 2026 | 2 hours 49 minutes | National Airspace System |
| 7 January 2026 | 2 hours 44 minutes | Carrier |
| 28 December 2025 | 2 hours 30 minutes | Late-arriving aircraft |
| 21 March 2026 | 1 hour 54 minutes | Carrier |
Delay causes
Why Spirit runs late on this route
National Airspace System accounts for 46% of the 2,134 delay minutes carriers reported here, and the remaining four split what is left.
- 46%National Airspace System
- 31%Late-arriving aircraft
- 22%Carrier
- 1%Extreme weather
46% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 983 minutes out of 2,134, against a national NAS share of 21%. The split is drawn from 2,134 reported delay minutes.
Cancellations run at 4.23%, against 1.89% nationally. That is about 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 stage length
What a delay here costs
11.9% 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.
The return leg is a different operation and performs like one: it runs 52.7% on time across 143 flights, 21 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 21 points of difference.
One caution: this is a thin sample. 142 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 Spirit on SJU to BOS
Put together: the delay figures matter less here than the 4.23% cancellation rate. A late arrival costs you about an hour; a cancelled flight costs you the day. Book the 11am–2pm departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 135 completed flights over 12 months sit behind that.
Related
Where to go next
- SJU to BOS, every carrier
- Spirit on BOS to SJU, the return leg
- Delta Air Lines on SJU to BOS77.4%
- JetBlue Airways on SJU to BOS68.5%
- Spirit Airlines network-wide record
- Luis Munoz Marin International (SJU) delay statistics
- Boston Logan International (BOS) delay statistics
- The US routes with the most cancellations
- What a cancellation rate actually tells you (and what it hides)
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.