Carrier route record
WNPBI→ISP
Southwest Airlines · West Palm Beach to Islip
- Flights
- 523
- Period
- September 2025 to August 2026
- Share of route
- 46%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on PBI to ISP sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.3%. The late ones land roughly 55 minutes behind schedule. That rests on 523 flights, with a median arrival right on schedule.
The US average over the same twelve months is 77.3%, so there is little to separate Southwest on PBI to ISP from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
73.9%
Arrivals under 15 minutes late, of 517 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
1.15%
National rate is 1.89%
Whole route
73.9%
Every carrier on PBI to ISP, 1,134 flights
These figures cover 523 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
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Carrier by carrier
Southwest against every carrier on PBI to ISP
Southwest flew 523 of the 1,134 flights on PBI to ISP, about 46% of it. Its 73.9% on time is about level with the route as a whole at 73.9%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from JetBlue at 76.8% to Frontier at 50.0%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| JetBlue Airways | 542 | 76.8% | 65 min | 1.85% | B |
| Southwest Airlines (this page) | 523 | 73.9% | 53 min | 1.15% | C |
| Frontier Airlinesthin sample | 69 | 50.0% | 67 min | 5.80% | F− |
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 Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 36 points, against half a point between the best and worst carrier.
- 5am–8am11 flights—
- 8am–11am73 flights84.9%
- 11am–2pm229 flights82.3%
- 2pm–5pm90 flights72.2%
- 5pm–8pm91 flights49.4%
- 8pm–5am29 flights—
Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 49.4% on time, against 84.9% for the 8am–11am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 11am–2pm window is the busiest, with 229 flights scheduled in it.
Across the year
Southwest on PBI to ISP through the year
October is the best month on the calendar at 91.8% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. December was the busiest month here, with 64 flights.
Across the week, Saturday is the strongest day at 80.3% on time and Thursday the weakest at 67.1%, a spread of 13 points.
Arrival by arrival
How late Southwest on PBI to ISP runs when it is late
The 135 late arrivals split 50 under half an hour, 50 between 30 and 60 minutes, and 35 an hour or more.
- 15+ min early74 flights14.3%
- Within 15 min308 flights59.6%
- 15–29 min late50 flights9.7%
- 30–59 min late50 flights9.7%
- 1–2 hours late22 flights4.3%
- 2+ hours late13 flights2.5%
Scale runs 0% to 100%.
Share of 517 completed flights by arrival against schedule.
30 of 143 late departures made up the time and arrived on time, 21% of them. 22 flights left on time and still arrived late.
The worst days
Worst days for Southwest on PBI to ISP
The latest arrival of the period was on 8 November 2025, 6 hours 49 minutes behind schedule; most of its delay minutes were filed as national airspace system delay. On three of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 8 November 2025 | 6 hours 49 minutes | National Airspace System |
| 2 March 2026 | 4 hours 6 minutes | Carrier |
| 9 November 2025 | 3 hours 45 minutes | Late-arriving aircraft |
| 3 February 2026 | 3 hours 2 minutes | Late-arriving aircraft |
| 23 May 2026 | 2 hours 47 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 61% of the 7,176 delay minutes carriers reported here, and the remaining four split what is left.
- 61%Late-arriving aircraft
- 22%Carrier
- 16%National Airspace System
- 1%Extreme weather
61% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 7,176 reported delay minutes here, that single category outweighs weather by 44 to one. The split is drawn from 7,176 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 84.9% on time here.
Cancellations sit at 1.15% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
6.8% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last roughly 55 minutes, which a normal layover absorbs.
The 1,052 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.
The return leg is a different operation and performs like one: it runs 70.7% on time across 524 flights, 3 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 3 points of difference.
One caution: this is a thin sample. 523 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 Southwest on PBI to ISP
Put together: treat all of this as provisional. 523 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 73.9% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 517 completed flights over 12 months sit behind that.
Related
Where to go next
- PBI to ISP, every carrier
- Southwest on ISP to PBI, the return leg
- JetBlue Airways on PBI to ISP76.8%
- Southwest Airlines network-wide record
- Palm Beach International (PBI) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.