Carrier route record
WNISP→PBI
Southwest Airlines · Islip to West Palm Beach
- Flights
- 524
- 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 ISP to PBI sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.3%. The late ones land about 50 minutes behind schedule. That rests on 524 flights, with a median arrival 3 minutes late.
The national on-time rate over the same period is 77.3%, so Southwest on ISP to PBI runs 7 points behind the country as a whole. Across a thousand flights that is about 66 extra late arrivals.
Key figures
On time
70.7%
Arrivals under 15 minutes late, of 515 completed flights
Avg delay
50 min
Across delayed arrivals only, not all flights
Cancelled
1.72%
National rate is 1.89%
Whole route
72.1%
Every carrier on ISP to PBI, 1,133 flights
These figures cover 524 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 ISP to PBI
Southwest flew 524 of the 1,133 flights on ISP to PBI, about 46% of it. Its 70.7% on time is about level with the route as a whole at 72.1%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from JetBlue at 73.7% to Frontier at 69.7%. 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 | 540 | 73.7% | 95 min | 2.59% | C |
| Southwest Airlines (this page) | 524 | 70.7% | 50 min | 1.72% | C |
| Frontier Airlinesthin sample | 69 | 69.7% | 86 min | 4.35% | C− |
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 29 points, against half a point between the best and worst carrier.
- 5am–8am153 flights85.2%
- 8am–11am47 flights80.9%
- 11am–2pm147 flights69.4%
- 2pm–5pm166 flights55.9%
- 5pm–8pm5 flights—
- 8pm–5am6 flights—
Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 85.2% of the time, against 55.9% for the afternoon window. That is 29 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 166 flights scheduled in it.
Across the year
Southwest on ISP to PBI through the year
December is the weak month at 50.8% on time, against 83.9% in October. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. December was the busiest month here, with 64 flights.
Across the week, Friday is the strongest day at 79.7% on time and Monday the weakest at 63.9%, a spread of 16 points.
Arrival by arrival
How late Southwest on ISP to PBI runs when it is late
The 151 late arrivals split 63 under half an hour, 56 between 30 and 60 minutes, and 32 an hour or more.
- 15+ min early72 flights14.0%
- Within 15 min292 flights56.7%
- 15–29 min late63 flights12.2%
- 30–59 min late56 flights10.9%
- 1–2 hours late23 flights4.5%
- 2+ hours late9 flights1.7%
Scale runs 0% to 100%.
Share of 515 completed flights by arrival against schedule.
A late pushback is often recovered here: of 164 departures that left 15 minutes late or more, 51 still arrived on time. In the other direction, 38 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 PBI.
The worst days
Worst days for Southwest on ISP to PBI
The latest arrival of the period was on 8 November 2025, 4 hours 57 minutes behind schedule; most of its delay minutes were filed as national airspace system delay. The five worst days are spread across November, December and January, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 8 November 2025 | 4 hours 57 minutes | National Airspace System |
| 28 November 2025 | 4 hours 45 minutes | Carrier |
| 26 December 2025 | 4 hours 45 minutes | Extreme weather |
| 5 January 2026 | 3 hours 33 minutes | Carrier |
| 21 December 2025 | 3 hours 22 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 7,486 reported delay minutes.
- 39%Carrier
- 31%Late-arriving aircraft
- 27%National Airspace System
- 4%Extreme weather
The largest share of delay minutes, 39%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,905 of the 7,486 delay minutes reported here. The split is drawn from 7,486 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 85.2% on time here.
Cancellations sit at 1.72% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
6.2% 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 about 50 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 73.9% on time across 523 flights, 3 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 3 points of difference.
One caution: this is a thin sample. 524 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 ISP to PBI
Put together: treat all of this as provisional. 524 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 70.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 515 completed flights over 12 months sit behind that.
Related
Where to go next
- ISP to PBI, every carrier
- Southwest on PBI to ISP, the return leg
- JetBlue Airways on ISP to PBI73.7%
- Southwest Airlines network-wide record
- Palm Beach International (PBI) delay statistics
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
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.