Carrier route record

DLJFK→SJU

Delta Air Lines · New York to San Juan

Flights: 1,104
Period: July 2025 to June 2026
Share of route: 30%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on JFK to SJU lands a B, about a point better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,104 flights, with a median arrival 10 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Delta on JFK to SJU from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

78.8%

Arrivals under 15 minutes late, of 1,080 completed flights

Avg delay

60 min

Across delayed arrivals only, not all flights

Cancelled

1.99%

National rate is 1.81%

Whole route

71.1%

Every carrier on JFK to SJU, 3,651 flights

These figures cover 1,104 flights between July 2025 and June 2026. The median arrival is 10 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Delta against every carrier on JFK to SJU

Delta flew 1,104 of the 3,651 flights on JFK to SJU, about 30% of it. Its 78.8% on time is 8 points better than the route as a whole, which runs 71.1%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from Delta at 78.8% to Frontier at 56.1%. 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.

On-time performance by carrier on JFK to SJU
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)	1,104	78.8%	60 min	1.99%	B
JetBlue Airways	2,232	69.5%	74 min	2.91%	C
Frontier Airlinesthin sample	315	56.1%	99 min	2.86%	D

Flight by flight

Delta flight numbers on JFK to SJU

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 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–8am—
8am–11am365 flights82.5%
11am–2pm364 flights85.6%
2pm–5pm—
5pm–8pm322 flights67.3%
8pm–5am53 flights76.5%

Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.

The best window here is not the first bank but the 11am–2pm slot at 85.6% on time, ahead of 5pm–8pm at 67.3%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 8am–11am window is the busiest, with 365 flights scheduled in it.

Across the year

Delta on JFK to SJU through the year

Darker means more delays. Figures are on-time percentages.April best, January worst

January is the weak month at 69.0% on time, against 88.9% in April. 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 105 flights.

Across the week, Friday is the strongest day at 85.1% on time and Thursday the weakest at 70.7%. 14 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 46% of the 14,000 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.

Carrier
46%
National Airspace System
35%
Late-arriving aircraft
16%
Extreme weather
3%
Security
1%

The largest share of delay minutes, 46%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 6,295 of the 14,000 delay minutes reported here. The split is drawn from 13,635 reported delay minutes.

35% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 4,720 minutes out of 14,000, against a national NAS share of 21%.

Cancellations sit at 1.99% against a national 1.81%, which is ordinary. Diversions add another 0.18%.

Connections and stage length

What a delay here costs

6.7% 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.

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 88.8% on time across 1,104 flights, 10 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 10 points of difference.

The sample behind these figures is 1,104 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.

What to do with this

Booking Delta on JFK to SJU

Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 88.9% on time and January 69.0%, a swing of 20 points. If the dates move at all, move them out of January before you think about anything else. 1,080 completed flights over 12 months sit behind that.

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.

Key figures