Carrier route record
NKFLL→BOS
Spirit Airlines · Fort Lauderdale to Boston
- Flights
- 570
- Period
- July 2025 to June 2026
- Share of route
- 17%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Spirit Airlines.
Spirit on FLL to BOS draws a D−. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is a little over an hour behind schedule. Build slack into anything you connect to. That rests on 570 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 884 at 71.8% on time.
The national on-time rate over the same period is 77.6%, so Spirit on FLL to BOS runs 16 points behind the country as a whole. Across a thousand flights that is about 159 extra late arrivals.
Key figures
On time
61.7%
Arrivals under 15 minutes late, of 543 completed flights
Avg delay
77 min
Across delayed arrivals only, not all flights
Cancelled
4.74%
National rate is 1.81%
Whole route
66.5%
Every carrier on FLL to BOS, 3,406 flights
These figures cover 570 flights between July 2025 and June 2026. Beyond the headline rate, 17.1% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Spirit against every carrier on FLL to BOS
Spirit flew 570 of the 3,406 flights on FLL to BOS, about 17% of it. Its 61.7% on time is 5 points worse than the route as a whole, which runs 66.5%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from Delta at 71.8% to Spirit at 61.7%.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 71.8% of the time; JetBlue Airways manages 65.6%. Sample sizes sit next to every figure, because a two-point gap across 1,952 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 884 | 71.8% | 79 min | 3.05% | C− |
| JetBlue Airways | 1,952 | 65.6% | 78 min | 2.92% | C |
| Spirit Airlines (this page) | 570 | 61.7% | 77 min | 4.74% | D− |
Delta Air Lines cancels 3.0% 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.
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 44 points, against 6 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am45 flights60.0%
- 8am–11am95 flights88.3%
- 11am–2pm66 flights52.5%
- 2pm–5pm65 flights44.3%
- 5pm–8pm7 flights—
- 8pm–5am292 flights58.5%
Scale runs 35% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 88.3% of the time, against 44.3% for the afternoon window. That is 44 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 292 flights scheduled in it.
Across the year
Spirit on FLL to BOS through the year
September is the best month on the calendar at 86.7% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. February was the busiest month here, with 69 flights.
Across the week, Wednesday is the strongest day at 68.0% on time and Sunday the weakest at 49.3%. 19 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Spirit runs late on this route
One category carries most of the weight here. National Airspace System accounts for 45% of the 16,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 45%National Airspace System
- 31%Carrier
- 23%Late-arriving aircraft
- 1%Extreme weather
- 0%Security
45% 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 7,219 minutes out of 16,000, against a national NAS share of 21%. The split is drawn from 16,081 reported delay minutes.
Cancellations run at 4.74%, against 1.81% nationally. That is about one flight in twenty 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 17.1% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
The 1,237 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 64.6% on time across 571 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 570 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 FLL to BOS
Put together: the delay figures matter less here than the 4.74% cancellation rate. A late arrival costs you a little over an hour; a cancelled flight costs you the day. Book the 8am–11am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 543 completed flights over 12 months sit behind that.
Related
Where to go next
- FLL to BOS, every carrier
- Spirit on BOS to FLL, the return leg
- Delta Air Lines on FLL to BOS71.8%
- JetBlue Airways on FLL to BOS65.6%
- Spirit Airlines network-wide record
- Fort Lauderdale-Hollywood International (FLL) 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.