Route reliability record
JFK→SJU
New York to San Juan
- Flights
- 3,554
- Period
- September 2025 to August 2026
- Distance
- 1,598 mi
- Carriers
- 3
This route carries a cancellation problem, not just a delay problem: 3.6% of scheduled flights never operate, against 1.9% nationally. Of the ones that do fly, about seven flights in ten arrive on time, worth a C− overall. The punctuality figure counts only flights that actually departed, so it flatters an operation that cancels this often. That rests on 3,554 JFK to SJU flights, of which Delta Air Lines flew 1,104 at 77.4% on time.
Best time to fly JFK to SJU: a 5am–8am departure, ideally on a Friday. Flights in that window arrived on time 81.2% of the time and Friday flights 74.8%, against 70.2% for the route overall.
The national on-time rate over the same period is 77.3%, so this route runs 7 points behind the country as a whole. Across a thousand flights that is about 71 extra late arrivals.
Key figures
On time
70.2%
Arrivals under 15 minutes late, of 3,423 completed flights
Avg delay
78 min
Across delayed arrivals only, not all flights
Cancelled
3.57%
National rate is 1.89%
Best carrier
Delta
77.4% on time across 1,104 flights
These figures cover 3,554 flights between September 2025 and August 2026. Beyond the headline rate, 12.5% 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 JFK to SJU
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 77.4% of the time; JetBlue Airways manages 67.7%. Sample sizes sit next to every figure, because a two-point gap across 2,245 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,104 | 77.4% | 61 min | 2.26% | B |
| JetBlue Airways | 2,245 | 67.7% | 78 min | 4.14% | C− |
| Frontier Airlinesthin sample | 205 | 58.2% | 124 min | 4.39% | D− |
JetBlue Airways cancels 4.1% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Flight by flight
Flights on JFK to SJU
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 New York to San Juan
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. 2 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. JFK → SJUNew York to San Juan | Delta Air Lines | 75.7% | 77.4% | 2.26% | 11am–2pm, Fri | DL 1961 12:25 |
| 2. EWR → SJUNewark to San Juan | JetBlue Airways | 70.1% | 73.0% | 3.93% | 5am–8am, Wed | — |
| 3. EWR → SJUNewark to San Juan | United Airlines | 68.2% | 69.7% | 2.16% | 8am–11am, Tue | UA 1556 09:43 |
| 4. JFK → SJUNew York to San Juan | JetBlue Airways | 64.9% | 67.7% | 4.14% | 5am–8am, Tue | B6 1603 08:29 |
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 20 points, against 10 points between the best and worst carrier.
- 5am–8am411 flights81.2%
- 8am–11am816 flights74.2%
- 11am–2pm866 flights74.1%
- 2pm–5pm231 flights66.1%
- 5pm–8pm761 flights62.2%
- 8pm–5am469 flights61.2%
Scale runs 55% to 85%.
The 8pm–5am window is where this operation falls apart: 61.2% on time, against 81.2% for the 5am–8am 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 866 flights scheduled in it.
Explore
Filter JFK to SJU 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 JFK to SJU, the best departure window is 5am–8am at 81.2% on time and the worst is 8pm–5am at 61.2%, a wide gap of 20.0 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am81.2%
- 8–11am74.2%
- 11am–2pm74.1%
- 2–5pm66.1%
- 5–8pm62.2%
- 8pm–5am61.2%
best all US flightsScale 55% to 95%.
Across the year
When delays peak on this route
This route's year swings by 30 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.
July is the worst month at 51.9% on time, 30 points below May, the best at 82.2%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. December was the busiest month here, with 350 flights.
Across the week, Friday is the strongest day at 74.8% on time and Sunday the weakest at 64.4%, a spread of 10 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 79,000 reported delay minutes.
- 40%Late-arriving aircraft
- 34%Carrier
- 24%National Airspace System
- 2%Extreme weather
- 1%Security
40% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 79,000 reported delay minutes here, that single category outweighs weather by 19 to one. The split is drawn from 79,149 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 81.2% on time here.
Cancellations run at 3.57%, against 1.89% nationally. That is about one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and stage length
What a delay here actually costs
12.5% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
At 1,598 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 77.8% on time across 3,560 flights, 8 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 8 points of difference.
The sample behind these figures is 3,554 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 SJU after this flight
What to do with this
Booking this route
Put together: the delay figures matter less here than the 3.57% cancellation rate. A late arrival costs you a little over an hour; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 3,423 completed flights over 12 months sit behind that.
Common questions
JFK to SJU questions
How often is JFK to SJU delayed?
Roughly one flight in three arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 29.8% of the 3,554 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 JFK to SJU?
Delta Air Lines leads at 77.4% on time across 1,104 flights. JetBlue Airways is at the other end on 67.7%, a gap of 10 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 JFK to SJU?
The 5am–8am departure window is the strongest at 81.2% on time. The 8pm–5am window is the weakest at 61.2%, 20 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 July delays on JFK to SJU?
July is the weakest month at 51.9% on time, compared with 82.2% in May. Across the year that is 30 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
- SJU to JFK — the return legseparate record
- John F. Kennedy International (JFK) delay statistics
- Luis Munoz Marin International (SJU) delay statistics
- Delta Air Lines on JFK to SJU77.4%
- JetBlue Airways on JFK to SJU67.7%
- Frontier Airlines on JFK to SJU58.2%
- JFK to LAX, a related route75.4%
- MCO to SJU, a related route73.8%
- JFK to SFO, a related route71.4%
- Delta Air Lines on-time record77.4%
- JetBlue Airways on-time record67.7%
- Frontier Airlines on-time record58.2%
- The US routes with the most cancellations
- Why the first flight of the morning is statistically safest
Direction matters. JFK to SJU and SJU to JFK 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.