Route reliability record
ATL→SJU
Atlanta to San Juan
- Flights
- 2,130
- Period
- July 2025 to June 2026
- Distance
- 1,547 mi
- Carriers
- 3
This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 2,130 flights, of which Delta Air Lines flew 1,636 at 75.8% on time.
The national on-time rate over the same period is 77.6%, 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
70.5%
Arrivals under 15 minutes late, of 2,099 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
1.27%
National rate is 1.81%
Best carrier
Delta
75.8% on time across 1,636 flights
These figures cover 2,130 flights between July 2025 and June 2026. Beyond the headline rate, 8.4% 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 airline is most reliable on ATL to SJU
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 75.8% of the time; Frontier Airlines manages 54.7%. Sample sizes sit next to every figure, because a two-point gap across 369 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,636 | 75.8% | 51 min | 0.92% | B+ |
| Frontier Airlines | 369 | 54.7% | 75 min | 1.63% | F |
| Spirit Airlinesthin sample | 125 | 46.2% | 56 min | 4.80% | F− |
The spread between Delta and Frontier is 21 points, wide enough that it should decide the booking. On a hundred trips that is 21 more arrivals inside the on-time window.
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 32 points, against 21 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am43 flights85.7%
- 8am–11am993 flights73.4%
- 11am–2pm433 flights77.1%
- 2pm–5pm121 flights53.8%
- 5pm–8pm464 flights63.5%
- 8pm–5am76 flights55.4%
Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 85.7% of the time, against 53.8% for the afternoon window. That is 32 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 993 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 20 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.
Delays peak in March, when the on-time rate falls to 61.0%. June is the strongest month at 80.5%. Moving a flexible trip across that boundary buys 20 points. March was the busiest month here, with 230 flights.
Across the week, Wednesday is the strongest day at 82.3% on time and Saturday the weakest at 62.7%. 20 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Carrier accounts for 48% of the 36,000 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.
- 48%Carrier
- 28%Late-arriving aircraft
- 23%National Airspace System
- 2%Extreme weather
- 0%Security
The largest share of delay minutes, 48%, 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 17,000 of the 36,000 delay minutes reported here. The split is drawn from 35,850 reported delay minutes.
Cancellations sit at 1.27% against a national 1.81%, which is ordinary. Diversions add another 0.19%.
Connections and stage length
What a delay here actually costs
8.4% 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 about an hour kind, which a normal layover absorbs.
At 1,547 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 82.0% on time across 2,126 flights, 12 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 12 points of difference.
The sample behind these figures is 2,130 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 this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. June runs 80.5% on time and March 61.0%, a swing of 20 points. If the dates move at all, move them out of March before you think about anything else. 2,099 completed flights over 12 months sit behind that.
Common questions
ATL to SJU questions
How often is ATL to SJU delayed?
Roughly one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 29.5% of the 2,130 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ATL to SJU?
Delta Air Lines leads at 75.8% on time across 1,636 flights. Frontier Airlines is at the other end on 54.7%, a gap of 21 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 ATL to SJU?
The 5am–8am departure window is the strongest at 85.7% on time. The 2pm–5pm window is the weakest at 53.8%, 32 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 March delays on ATL to SJU?
March is the weakest month at 61.0% on time, compared with 80.5% in June. Across the year that is 20 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 ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Luis Munoz Marin International (SJU) delay statistics
- Delta Air Lines on-time record75.8%
- Frontier Airlines on-time record54.7%
- Spirit Airlines on-time record46.2%
- The best time of day to fly, according to 7.04 million flight records
- Connecting flights: how much buffer the data says you need
Direction matters. ATL to SJU and SJU to ATL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.