Route reliability record
ATL→SJU
Atlanta to San Juan
- Flights
- 2,101
- Period
- September 2025 to August 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, 6 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 2,101 ATL to SJU flights, of which Delta Air Lines flew 1,638 at 76.9% on time.
Best time to fly ATL to SJU: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 85.7% of the time and Wednesday flights 82.0%, against 71.6% for the route overall.
The national on-time rate over the same period is 77.3%, so this route runs 6 points behind the country as a whole. Across a thousand flights that is about 57 extra late arrivals.
Key figures
On time
71.6%
Arrivals under 15 minutes late, of 2,071 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
1.29%
National rate is 1.89%
Best carrier
Delta
76.9% on time across 1,638 flights
These figures cover 2,101 flights between September 2025 and August 2026. Beyond the headline rate, 8.3% 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 ATL to SJU
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 76.9% of the time; Frontier Airlines manages 56.5%. Sample sizes sit next to every figure, because a two-point gap across 387 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,638 | 76.9% | 53 min | 0.85% | B+ |
| Frontier Airlines | 387 | 56.5% | 67 min | 1.81% | D |
| Spirit Airlinesthin sample | 76 | 30.0% | 62 min | 7.89% | F− |
The spread between Delta and Frontier is 20 points, wide enough that it should decide the booking. On a hundred trips that is 20 more arrivals inside the on-time window.
Flight by flight
Flights on ATL 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 Atlanta to San Juan
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ATL → SJUAtlanta to San Juan | Delta Air Lines | 76.2% | 76.9% | 0.85% | 5am–8am, Wed | DL 1757 08:05 |
| 2. ATL → SJUAtlanta to San Juan | Frontier Airlines | 55.5% | 56.5% | 1.81% | 8am–11am, Wed | F9 2082 10:25 |
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 31 points, against 20 points between the best and worst carrier.
- 5am–8am43 flights85.7%
- 8am–11am1,010 flights74.7%
- 11am–2pm398 flights78.6%
- 2pm–5pm115 flights55.9%
- 5pm–8pm460 flights64.0%
- 8pm–5am75 flights54.8%
Scale runs 45% to 90%.
The 8pm–5am window is where this operation falls apart: 54.8% on time, against 85.7% 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 8am–11am window is the busiest, with 1,010 flights scheduled in it.
Explore
Filter ATL 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 ATL to SJU, the best departure window is 5am–8am at 85.7% on time and the worst is 8pm–5am at 54.8%, a wide gap of 30.9 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am85.7%
- 8–11am74.7%
- 11am–2pm78.6%
- 2–5pm55.9%
- 5–8pm64.0%
- 8pm–5am54.8%
best all US flightsScale 45% to 95%.
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 82.0% on time and Sunday the weakest at 63.5%, a spread of 19 points.
Delay causes
Why this route gets delayed
Carrier accounts for 46% of the 34,000 delay minutes carriers reported here, and the remaining four split what is left.
- 46%Carrier
- 30%Late-arriving aircraft
- 23%National Airspace System
- 1%Extreme weather
- 0%Security
The largest share of delay minutes, 46%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 16,000 of the 34,000 delay minutes reported here. The split is drawn from 33,801 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 85.7% on time here.
Cancellations sit at 1.29% against a national 1.89%, which is ordinary. Diversions add another 0.14%.
Connections and stage length
What a delay here actually costs
8.3% of arrivals land an hour or more late, close to the national 8.3%, so 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 1,547 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 81.6% on time across 2,097 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 2,101 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 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. 2,071 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 four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 28.4% of the 2,101 flights in this analysis, against 22.7% 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 76.9% on time across 1,638 flights. Frontier Airlines is at the other end on 56.5%, a gap of 20 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 8pm–5am window is the weakest at 54.8%, 31 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 ATL to SJU76.9%
- Frontier Airlines on ATL to SJU56.5%
- ATL to LGA, a related route72.3%
- MCO to SJU, a related route73.8%
- ATL to MCO, a related route70.3%
- Delta Air Lines on-time record76.9%
- Frontier Airlines on-time record56.5%
- Spirit Airlines on-time record30.0%
- Same route, different airline: where the carrier you pick matters most
- The best time of day to fly, according to 7.05 million flight records
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.
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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.