84% of flights from Islip to Baltimore arrived on time over the past 12 months. That is better than the typical U.S. route. The 6 a.m. departures ran on time 95% of the time; the 5 p.m. ones 70%. 6% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for ISP → BWI: when a flight was late, it was under 45 minutes late 58% of the time. About 1 in 23 flights landed an hour or more late, and 1 in 63 three hours or more; 1.5% were cancelled outright.
- On time or early84%
- 15–30 min late5.8%
- 30–60 min late4.4%
- 1–2 hours late2.1%
- 2–3 hours late0.6%
- 3+ hours late1.6%
- Diverted0.2%
- Cancelled1.5%
Share of all 1,259 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| Southwest Airlines | 1,259 | 84% | 1.5% | −7 min | 4.4% | +71 min | Southwest Airlines |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at ISP). Delays build through the day as late planes knock on, so early flights usually do best.
Last flight of the day
On ISP → BWI, each airline's last flight of the day was cancelled 2.5% of the time, against 1.1% for its earlier flights (2.2× as often). It arrived 3+ hours late 3.0% of the time (earlier flights: 1.0%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| Southwest Airlines | 4:40 p.m. | 2.5% | 3.0% | 1.1% | first flight 6:00 a.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
If you need to be in BWI tonight, book an earlier flight so there's a backup if it's cancelled.
By month
Each calendar month pooled over 2023–2026. Best: September (93%). Worst: July (72%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 188 | 79% | 3.7% |
| Tuesday | 185 | 84% | 1.6% |
| Wednesday | 185 | 86% | 0.0% |
| Thursday | 186 | 84% | 0.5% |
| Friday | 186 | 89% | 0.5% |
| Saturday | 159 | 82% | 1.3% |
| Sunday | 170 | 82% | 2.9% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 11 · air traffic/airport 6 · airline 2
Month by month
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Feb 23, 2026 | 3 | 0% | 3 |
| Jan 25, 2026 | 3 | 0% | 3 |
| Mar 17, 2026 | 3 | 0% | 1 |
| Jul 22, 2026 | 5 | 20% | 0 |
| Jun 23, 2026 | 5 | 20% | 0 |
Nearby airport alternatives
Other ways to make the same trip, using airports within 60 miles of Islip or Baltimore. None has been clearly more reliable than ISP → BWI.
| Route | Flights | On time | Cancelled |
|---|---|---|---|
| ISP → BWI (this route) | 1,259 | 84% | 1.5% |
| EWR → IAD Newark to Washington Dulles | 1,826 | 72% | 3.0% |
| JFK → IAD New York JFK to Washington Dulles | 713 | 72% | 5.2% |
| LGA → IAD LaGuardia to Washington Dulles | 1,450 | 69% | 7.1% |
| LGA → DCA LaGuardia to Washington Reagan National | 4,841 | 62% | 5.8% |
| JFK → DCA New York JFK to Washington Reagan National | 2,761 | 62% | 6.5% |
| EWR → DCA Newark to Washington Reagan National | 3,247 | 59% | 5.7% |
Questions
How often are flights from ISP to BWI on time?
84% of 1,259 scheduled flights from Islip, NY to Baltimore, MD arrived within 15 minutes of schedule between September 2025 and August 2026. 1.5% were cancelled.
What is the best time of day to fly ISP to BWI?
Flights scheduled to leave at 6 a.m. were the most reliable (95% on time). The 5 p.m. departures were the least (70%).
What month has the most delays from ISP to BWI?
July (72% on time). The best month is September (93%), over 2023–2026.
Is the last flight of the day from ISP to BWI more likely to be cancelled?
Yes. Each airline's last ISP–BWI flight of the day was cancelled 2.5% of the time over the past year, against 1.1% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- BWI → ISP (return)
- Long Island MacArthur (ISP) delays by hour
- Flights into Baltimore/Washington (BWI)
- Southwest Airlines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.