San Juan, PR · departure reliability

SJU

Luis Munoz Marin International

Departures: 35,391
Period: July 2025 to June 2026
Carriers: 7
US rank: #47 by volume

Terminal building and aircraft stands at a US airport

San Juan

Luis Munoz Marin International lands a B, level with the national rate of 77.6%. Roughly one flight in five arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 35,391 flights, of which Delta Air Lines flew 3,636 at 87.9% on time.

Delta Air Lines is the most reliable of the seven carriers covered here at 87.9% on time across 3,636 flights.

On time

77.8%

Departures arriving under 15 minutes late at their destination

Avg delay

77 min

Across delayed flights only

Cancelled

1.83%

National rate is 1.81%

Best carrier

Delta

87.9% on time here

These figures cover 35,000 flights between July 2025 and June 2026. The median arrival is 6 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

Which airlines run best out of SJU

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 87.9% of the time; Frontier Airlines manages 71.6%. Sample sizes sit next to every figure, because a two-point gap across 4,867 flights means less than a ten-point one.

On-time performance by carrier departing SJU
Airline	Flights	On time	Avg delay	Cancelled	Grade
JetBlue Airways	11,772	74.9%	75 min	1.90%	C
American Airlines	4,897	80.2%	96 min	1.39%	B
Frontier Airlines	4,867	71.6%	93 min	2.30%	C
Southwest Airlines	3,905	80.3%	48 min	0.79%	B+
Delta Air Lines	3,636	87.9%	73 min	1.51%	A
United Airlines	3,591	83.7%	67 min	1.23%	B
Spirit Airlines	2,723	71.7%	76 min	4.19%	C−

Spirit Airlines cancels 4.2% 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.

Route by route

Busiest routes out of SJU

Route-level records vary far more than the airport average. These are the 20 busiest departures from SJU, each with its own on-time rate against the airport-wide 77.8%.

Busiest routes from SJU by flight volume
Route	Flights	On time	Avg delay	Cancelled	Grade
SJU to MCO · Orlando	6,048	78.9%	79 min	1.01%	B
SJU to JFK · New York	3,657	79.3%	77 min	2.68%	B
SJU to MIA · Miami	2,642	77.7%	94 min	0.95%	B+
SJU to FLL · Fort Lauderdale	2,342	75.1%	72 min	1.41%	B
SJU to ATL · Atlanta	2,126	82.0%	82 min	1.36%	B
SJU to EWR · Newark	2,100	74.6%	83 min	3.14%	C−
SJU to BOS · Boston	2,001	71.8%	72 min	2.75%	C
SJU to PHL · Philadelphia	1,881	70.5%	84 min	3.40%	C−
SJU to TPA · Tampa	1,478	76.9%	71 min	1.49%	B
SJU to ORD · Chicago	1,397	79.5%	69 min	2.15%	B
SJU to BWI · Baltimore	1,184	77.9%	60 min	2.45%	B
SJU to CLT · Charlotte	1,077	85.6%	106 min	1.67%	A
SJU to DFW · Dallas-Fort Worth	993	78.7%	83 min	2.32%	B
SJU to BDL · Hartford	961	70.9%	73 min	1.87%	C
SJU to IAH · Houston	948	87.7%	55 min	0.63%	A+
SJU to IAD · Washington	697	86.0%	72 min	0.72%	A+
SJU to RDU · Raleigh	471	83.4%	72 min	1.70%	B
SJU to DTW · Detroit	384	83.2%	50 min	1.82%	B
SJU to STT · Charlotte Amalie	365	70.4%	74 min	0.55%	C+
SJU to DCA · Washington	365	69.9%	87 min	1.37%	C

Departure window

The best time of day to leave SJU

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 19 points, against 16 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am7,543 flights89.2%
8am–11am3,117 flights86.2%
11am–2pm5,577 flights78.1%
2pm–5pm8,445 flights72.3%
5pm–8pm6,342 flights71.9%
8pm–5am4,367 flights70.7%

Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 89.2% of the time, against 70.7% for the overnight 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 8,445 flights scheduled in it.

Across the year

When SJU runs late

SJU's year swings by 14 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.

Darker means more delays. Figures are on-time percentages.May best, August worst

August is the worst month at 70.9% on time, 14 points below May, the best at 84.7%. 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. March was the busiest month here, with 3,441 flights.

Across the week, Wednesday is the strongest day at 81.7% on time and Sunday the weakest at 73.4%. 8 points is a smaller lever than departure hour, but it is free.

Delay causes

Why SJU gets delayed

One category carries most of the weight here. Late-arriving aircraft accounts for 52% of the 593,000 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.

Late-arriving aircraft
52%
Carrier
34%
National Airspace System
13%
Extreme weather
1%
Security
0%

52% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 593,000 reported delay minutes here, that single category outweighs weather by 42 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 593,418 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 89.2% on time here.

Cancellations sit at 1.83% against a national 1.81%, which is ordinary. Diversions add another 0.38%.

7.9% 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 are the a little over an hour kind, which a normal layover absorbs.

35,391 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.

What to do with this

Flying out of SJU

Put together: the calendar is the biggest lever here, not the carrier or the hour. May runs 84.7% on time and August 70.9%, a swing of 14 points. If the dates move at all, move them out of August before you think about anything else. 34,607 completed flights over 12 months sit behind that.

Common questions

SJU delay questions

How often is San Juan (SJU) delayed?

Roughly one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.2% of the 35,391 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on San Juan (SJU)?

Delta Air Lines leads at 87.9% on time across 3,636 flights. Frontier Airlines is at the other end on 71.6%, a gap of 16 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 San Juan (SJU)?

The 5am–8am departure window is the strongest at 89.2% on time. The 8pm–5am window is the weakest at 70.7%, 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 August delays on San Juan (SJU)?

August is the weakest month at 70.9% on time, compared with 84.7% in May. Across the year that is 14 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures