Carrier route record
NKBOS→SJU
Spirit Airlines · Boston to San Juan
- Flights
- 143
- Period
- September 2025 to August 2026
- Share of route
- 8%
- Carriers
- 4
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Spirit Airlines.
Spirit on BOS to SJU earns an F−, which is as low as this site's scale goes for a reason. Only 52.7% of flights arrive inside the 15-minute window, 25 points worse than the national rate of 77.3%. Late arrivals average close to two hours. Treat any tight connection here as a coin flip. That rests on 143 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 398 at 74.5% on time.
The national on-time rate over the same period is 77.3%, so Spirit on BOS to SJU runs 25 points behind the country as a whole. Across a thousand flights that is about 246 extra late arrivals.
Key figures
On time
52.7%
Arrivals under 15 minutes late, of 131 completed flights
Avg delay
108 min
Across delayed arrivals only, not all flights
Cancelled
8.39%
National rate is 1.89%
Whole route
66.8%
Every carrier on BOS to SJU, 1,717 flights
These figures cover 143 flights between September 2025 and August 2026. Beyond the headline rate, 21.4% 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 BOS to SJU
Spirit flew 143 of the 1,717 flights on BOS to SJU, about 8% of it. Its 52.7% on time is 14 points worse than the route as a whole, which runs 66.8%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from Delta at 74.5% to Frontier at 42.4%. 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 74.5% of the time; JetBlue Airways manages 66.5%. Sample sizes sit next to every figure, because a two-point gap across 1,142 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 398 | 74.5% | 57 min | 1.51% | C |
| JetBlue Airways | 1,142 | 66.5% | 73 min | 2.80% | C |
| Spirit Airlines (this page)thin sample | 143 | 52.7% | 108 min | 8.39% | F− |
| Frontier Airlinesthin sample | 34 | 42.4% | 113 min | 2.94% | F |
Delta leads JetBlue by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh 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 is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 143 flights.
There are not enough flights in each departure window to split Spirit's BOS to SJU record by time of day without the percentages moving on noise. The headline rate of 52.7% is the reliable figure here.
Across the year
Spirit on BOS to SJU through the year
- Oct–Dec 202514 flights—
- Jan–Mar 2026101 flights52.2%
- Apr–Jun 202628 flights—
Scale runs 45% to 60%. 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 52.7% on time across 143 flights.
Split by quarter, Spirit on BOS to SJU logged 14 flights in Oct–Dec 2025, 101 flights in Jan–Mar 2026 and 28 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 52.7% annual figure is the one to use.
Arrival by arrival
How late Spirit on BOS to SJU runs when it is late
The 62 late arrivals split 16 under half an hour, 18 between 30 and 60 minutes, and 28 an hour or more.
- 15+ min early29 flights22.1%
- Within 15 min40 flights30.5%
- 15–29 min late16 flights12.2%
- 30–59 min late18 flights13.7%
- 1–2 hours late10 flights7.6%
- 2+ hours late18 flights13.7%
Scale runs 0% to 100%.
Share of 131 completed flights by arrival against schedule.
9 of 66 late departures made up the time and arrived on time, 14% of them. 5 flights left on time and still arrived late.
The worst days
Worst days for Spirit on BOS to SJU
The latest arrival of the period was on 24 February 2026, 20 hours 1 minute behind schedule; most of its delay minutes were filed as national airspace system delay. Three of the five worst days fell in February 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 24 February 2026 | 20 hours 1 minute | National Airspace System |
| 24 February 2026 | 10 hours 31 minutes | National Airspace System |
| 22 February 2026 | 4 hours 44 minutes | Late-arriving aircraft |
| 18 December 2025 | 4 hours 16 minutes | Late-arriving aircraft |
| 21 April 2026 | 4 hours 10 minutes | Carrier |
Delay causes
Why Spirit runs late on this route
National Airspace System accounts for 47% of the 6,670 delay minutes carriers reported here, and the remaining four split what is left.
- 47%National Airspace System
- 31%Carrier
- 20%Late-arriving aircraft
- 1%Extreme weather
47% 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 3,161 minutes out of 6,670, against a national NAS share of 21%. The split is drawn from 6,670 reported delay minutes.
Cancellations run at 8.39%, against 1.89% nationally. That is about one flight in twelve 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
21.4% 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 73.3% on time across 142 flights, 21 points above 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. 143 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 BOS to SJU
Put together: the delay figures matter less here than the 8.39% cancellation rate. A late arrival costs you close to two hours; a cancelled flight costs you the day. Book the 2pm–5pm departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 131 completed flights over 12 months sit behind that.
Related
Where to go next
- BOS to SJU, every carrier
- Spirit on SJU to BOS, the return leg
- Delta Air Lines on BOS to SJU74.5%
- JetBlue Airways on BOS to SJU66.5%
- Spirit Airlines network-wide record
- Boston Logan International (BOS) delay statistics
- Luis Munoz Marin International (SJU) 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.