Carrier route record
WNPBI→ISP
Southwest Airlines · West Palm Beach to Islip
- Flights
- 610
- Period
- July 2025 to June 2026
- Share of route
- 50%
- Carriers
- 3
Historical statistics for July 2025 to June 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+. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 610 flights, with a median arrival right on schedule.
The national on-time rate over the same period is 77.6%, so Southwest on PBI to ISP runs 5 points behind the country as a whole. Across a thousand flights that is about 48 extra late arrivals.
Key figures
On time
72.8%
Arrivals under 15 minutes late, of 604 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
0.98%
National rate is 1.81%
Whole route
73.6%
Every carrier on PBI to ISP, 1,223 flights
These figures cover 610 flights between July 2025 and June 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.
Carrier by carrier
Southwest against every carrier on PBI to ISP
Southwest flew 610 of the 1,223 flights on PBI to ISP, about 50% of it. Its 72.8% on time is about level with the route as a whole at 73.6%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from JetBlue at 77.5% to Frontier at 48.5%. 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 | 77.5% | 65 min | 1.85% | B |
| Southwest Airlines (this page) | 610 | 72.8% | 59 min | 0.98% | C+ |
| Frontier Airlinesthin sample | 71 | 48.5% | 70 min | 5.63% | F− |
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 34 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am11 flights—
- 8am–11am96 flights83.3%
- 11am–2pm254 flights82.9%
- 2pm–5pm119 flights65.5%
- 5pm–8pm101 flights49.5%
- 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: 49.5% on time, against 83.3% 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 254 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 81.5% on time and Thursday the weakest at 64.0%. 18 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 62% of the 9,598 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.
- 62%Late-arriving aircraft
- 21%Carrier
- 15%National Airspace System
- 2%Extreme weather
62% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 9,598 reported delay minutes here, that single category outweighs weather by 26 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 9,598 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 83.3% on time here.
Cancellations sit at 0.98% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
7.5% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, 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. 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 71.4% on time across 611 flights, within about a point 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. 610 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. 610 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 72.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 604 completed flights over 12 months sit behind that.
Related
Where to go next
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.