San Juan, PR · departure reliability
SJU
Luis Munoz Marin International
- Departures
- 35,483
- Period
- June 2025 to May 2026
- Carriers
- 7
- US rank
- #47 by volume
San Juan
Luis Munoz Marin International lands a B, level with the national rate of 77.4%. Roughly one flight in four 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 35,483 flights, of which Delta Air Lines flew 3,644 at 87.7% on time.
Delta Air Lines is the most reliable of the seven carriers covered here at 87.7% on time across 3,644 flights.
Key figures
On time
77.7%
Departures arriving under 15 minutes late at their destination
Avg delay
78 min
Across delayed flights only
Cancelled
1.86%
National rate is 1.80%
Best carrier
Delta
87.7% on time here
These figures cover 35,000 flights between June 2025 and May 2026. Beyond the headline rate, 8.0% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airlines run best out of SJU
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 87.7% of the time; Frontier Airlines manages 70.1%. Sample sizes sit next to every figure, because a two-point gap across 4,873 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| JetBlue Airways | 11,597 | 75.2% | 75 min | 1.87% | B |
| Frontier Airlines | 4,873 | 70.1% | 89 min | 2.50% | C |
| American Airlines | 4,844 | 79.8% | 103 min | 1.47% | B |
| Southwest Airlines | 3,924 | 80.9% | 47 min | 0.71% | B+ |
| Delta Air Lines | 3,644 | 87.7% | 73 min | 1.56% | A |
| United Airlines | 3,571 | 83.5% | 68 min | 1.37% | B |
| Spirit Airlines | 3,030 | 73.3% | 75 min | 3.80% | C− |
Spirit Airlines cancels 3.8% 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 77.7%.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SJU to MCO · Orlando | 6,034 | 79.4% | 77 min | 0.98% | B+ |
| SJU to JFK · New York | 3,718 | 79.3% | 77 min | 2.64% | B |
| SJU to MIA · Miami | 2,635 | 77.2% | 98 min | 1.18% | B |
| SJU to FLL · Fort Lauderdale | 2,340 | 75.3% | 73 min | 1.37% | B |
| SJU to ATL · Atlanta | 2,153 | 81.4% | 81 min | 1.44% | B |
| SJU to EWR · Newark | 2,119 | 74.0% | 84 min | 3.35% | C− |
| SJU to BOS · Boston | 2,028 | 72.4% | 71 min | 2.71% | C |
| SJU to PHL · Philadelphia | 1,834 | 68.8% | 87 min | 3.44% | C− |
| SJU to TPA · Tampa | 1,451 | 76.8% | 69 min | 1.45% | B |
| SJU to ORD · Chicago | 1,423 | 79.6% | 80 min | 2.11% | B |
| SJU to BWI · Baltimore | 1,209 | 77.1% | 60 min | 2.40% | B |
| SJU to CLT · Charlotte | 1,075 | 84.7% | 102 min | 1.77% | B |
| SJU to DFW · Dallas-Fort Worth | 1,030 | 80.0% | 81 min | 2.23% | B |
| SJU to IAH · Houston | 962 | 87.8% | 58 min | 0.73% | A+ |
| SJU to BDL · Hartford | 954 | 71.5% | 73 min | 1.89% | C |
| SJU to IAD · Washington | 688 | 85.2% | 70 min | 0.73% | A+ |
| SJU to RDU · Raleigh | 469 | 82.8% | 75 min | 1.92% | B |
| SJU to DTW · Detroit | 396 | 83.8% | 47 min | 1.52% | B |
| SJU to STT · Charlotte Amalie | 365 | 71.3% | 76 min | 0.55% | C+ |
| SJU to DCA · Washington | 365 | 70.5% | 86 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 18 points, against 18 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am7,393 flights89.3%
- 8am–11am3,102 flights86.0%
- 11am–2pm5,753 flights78.4%
- 2pm–5pm8,419 flights72.2%
- 5pm–8pm6,314 flights71.7%
- 8pm–5am4,502 flights70.9%
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 89.3% of the time, against 70.9% for the overnight window. That is 18 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
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.
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.
Across the week, Wednesday is the strongest day at 81.8% on time and Sunday the weakest at 73.6%. 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 50% of the 599,000 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.
- 50%Late-arriving aircraft
- 35%Carrier
- 13%National Airspace System
- 1%Extreme weather
- 0%Security
50% 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 599,000 reported delay minutes here, that single category outweighs weather by 40 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 largest share of delay minutes, 35%, 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 210,000 of the 599,000 delay minutes reported here.
Cancellations sit at 1.86% against a national 1.80%, which is ordinary. Diversions add another 0.39%.
8.0% of arrivals land an hour or more late, close to the national 8.2%. 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.
35,483 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.
Common questions
SJU delay questions
How often is San Juan (SJU) delayed?
Roughly one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.3% of the 35,483 flights in this analysis, against 22.6% 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 87.7% on time across 3,644 flights. Frontier Airlines is at the other end on 70.1%, a gap of 18 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 89.3% on time. The 8pm–5am window is the weakest at 70.9%, 18 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.
Related
Where to go next
- SJU to MCO — Orlando79.4%
- JetBlue Airways on-time record75.2%
- Frontier Airlines on-time record70.1%
- American Airlines on-time record79.8%
- Southwest Airlines on-time record80.9%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.