Route reliability record
ISP→PBI
Islip to West Palm Beach
- Flights
- 1,133
- Period
- September 2025 to August 2026
- Distance
- 1,052 mi
- Carriers
- 3
This route 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 77.3%. The late ones land a little over an hour behind schedule. That rests on 1,133 ISP to PBI flights, of which JetBlue Airways flew 540 at 73.7% on time.
Best time to fly ISP to PBI: a 5am–8am departure, ideally on a Friday. Flights in that window arrived on time 83.9% of the time and Friday flights 77.6%, against 72.1% for the route overall.
The national on-time rate over the same period is 77.3%, so this route runs 5 points behind the country as a whole. Across a thousand flights that is about 52 extra late arrivals.
Key figures
On time
72.1%
Arrivals under 15 minutes late, of 1,102 completed flights
Avg delay
72 min
Across delayed arrivals only, not all flights
Cancelled
2.29%
National rate is 1.89%
Best carrier
JetBlue
73.7% on time across 540 flights
These figures cover 1,133 flights between September 2025 and August 2026. Beyond the headline rate, 8.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on ISP to PBI
The two carriers here are closely matched: 3 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| JetBlue Airways | 540 | 73.7% | 95 min | 2.59% | C |
| Southwest Airlines | 524 | 70.7% | 50 min | 1.72% | C |
| Frontier Airlinesthin sample | 69 | 69.7% | 86 min | 4.35% | C− |
No carrier stands out. JetBlue tops the table at 73.7%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on ISP to PBI
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Islip to West Palm Beach
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 4 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. EWR → PBINewark to West Palm Beach | United Airlines | 77.7% | 79.4% | 2.10% | 5am–8am, Wed | UA 1771 06:30 |
| 2. JFK → PBINew York to West Palm Beach | Delta Air Lines | 77.1% | 80.9% | 4.65% | 5am–8am, Wed | DL 2018 07:00 |
| 3. EWR → FLLNewark to Fort Lauderdale | United Airlines | 76.2% | 78.2% | 2.53% | 5am–8am, Tue | UA 1364 07:00 |
| 4. JFK → FLLNew York to Fort Lauderdale | Delta Air Lines | 72.4% | 75.3% | 3.90% | 5am–8am, Tue | DL 1422 07:00 |
| 5. ISP → PBIIslip to West Palm Beach | JetBlue Airways | 71.8% | 73.7% | 2.59% | 5am–8am, Tue | B6 545 13:55 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 19 points, against 3 points between the best and worst carrier.
- 5am–8am249 flights83.9%
- 8am–11am72 flights81.7%
- 11am–2pm248 flights74.0%
- 2pm–5pm474 flights64.5%
- 5pm–8pm83 flights65.4%
- 8pm–5am7 flights—
Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 83.9% of the time, against 64.5% for the afternoon window. That is 19 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 474 flights scheduled in it.
Explore
Filter ISP to PBI by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On ISP to PBI, the best departure window is 5am–8am at 83.9% on time and the worst is 2pm–5pm at 64.5%, a wide gap of 19.4 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am83.9%
- 8–11am81.7%
- 11am–2pm74.0%
- 2–5pm64.5%
- 5–8pm65.4%
- 8pm–5am—
best all US flightsScale 55% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 29 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
December is the weak month at 57.3% on time, against 86.1% in June. 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. February was the busiest month here, with 133 flights.
Across the week, Friday is the strongest day at 77.6% on time and Sunday the weakest at 68.4%, a spread of 9 points.
Delay causes
Why this route gets delayed
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 22,000 reported delay minutes.
- 40%Late-arriving aircraft
- 30%Carrier
- 21%National Airspace System
- 9%Extreme weather
40% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 22,000 reported delay minutes here, that single category outweighs weather by 5 to one. The split is drawn from 22,227 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 83.9% on time here.
Cancellations sit at 2.29% against a national 1.89%, which is ordinary. Diversions add another 0.44%.
Connections and stage length
What a delay here actually costs
8.9% 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 a little over 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.
The return leg runs 73.9% on time across 1,134 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,133 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in PBI after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. June runs 86.1% on time and December 57.3%, a swing of 29 points. If the dates move at all, move them out of December before you think about anything else. 1,102 completed flights over 12 months sit behind that.
Common questions
ISP to PBI questions
How often is ISP to PBI delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.9% of the 1,133 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on ISP to PBI?
JetBlue Airways leads at 73.7% on time across 540 flights. Southwest Airlines is at the other end on 70.7%, a gap of 3 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on ISP to PBI?
The 5am–8am departure window is the strongest at 83.9% on time. The 2pm–5pm window is the weakest at 64.5%, 19 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are December delays on ISP to PBI?
December is the weakest month at 57.3% on time, compared with 86.1% in June. Across the year that is 29 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- PBI to ISP — the return legseparate record
- Palm Beach International (PBI) delay statistics
- JetBlue Airways on ISP to PBI73.7%
- Southwest Airlines on ISP to PBI70.7%
- ISP to MCO, a related route74.4%
- ATL to PBI, a related route75.8%
- ISP to BWI, a related route85.1%
- JetBlue Airways on-time record73.7%
- Southwest Airlines on-time record70.7%
- Frontier Airlines on-time record69.7%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. ISP to PBI and PBI to ISP are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.