Route reliability record
SJU→MIA
San Juan to Miami
- Flights
- 2,650
- Period
- September 2025 to August 2026
- Distance
- 1,045 mi
- Carriers
- 3
This route lands a B+, 2 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That rests on 2,650 SJU to MIA flights, of which Frontier Airlines flew 381 at 79.9% on time.
Best time to fly SJU to MIA: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 93.5% of the time and Wednesday flights 85.0%, against 78.9% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
78.9%
Arrivals under 15 minutes late, of 2,620 completed flights
Avg delay
89 min
Across delayed arrivals only, not all flights
Cancelled
0.94%
National rate is 1.89%
Best carrier
Frontier
79.9% on time across 381 flights
These figures cover 2,650 flights between September 2025 and August 2026. Beyond the headline rate, 8.7% 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 SJU to MIA
The two carriers here are closely matched: about a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlines | 381 | 79.9% | 96 min | 1.57% | B |
| American Airlines | 2,141 | 79.0% | 89 min | 0.70% | B+ |
| Spirit Airlinesthin sample | 128 | 73.4% | 81 min | 3.12% | C− |
No carrier stands out. Frontier tops the table at 79.9%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.
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Best ways to make this trip
The most reliable ways to fly San Juan to Miami
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 1 of the top 3 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SJU → MIASan Juan to Miami | Frontier Airlines | 78.6% | 79.9% | 1.57% | 5am–8am, Thu | — |
| 2. SJU → MIASan Juan to Miami | American Airlines | 78.4% | 79.0% | 0.70% | 5am–8am, Wed | — |
| 3. SJU → FLLSan Juan to Fort Lauderdale | JetBlue Airways | 76.9% | 77.9% | 1.34% | 5am–8am, Tue | B6 754 07:00 |
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 26 points, against about a point between the best and worst carrier.
- 5am–8am499 flights93.5%
- 8am–11am296 flights87.7%
- 11am–2pm727 flights81.9%
- 2pm–5pm493 flights68.2%
- 5pm–8pm542 flights67.7%
- 8pm–5am93 flights71.1%
Scale runs 60% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.5% of the time, against 67.7% for the evening window. That is 26 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 727 flights scheduled in it.
Explore
Filter SJU to MIA 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 SJU to MIA, the best departure window is 5am–8am at 93.5% on time and the worst is 5pm–8pm at 67.7%, a wide gap of 25.8 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am93.5%
- 8–11am87.7%
- 11am–2pm81.9%
- 2–5pm68.2%
- 5–8pm67.7%
- 8pm–5am71.1%
best all US flightsScale 60% to 100%.
Across the year
When delays peak on this route
This route's year swings by 15 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.
January is the weak month at 72.5% on time, against 87.4% in June. 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. March was the busiest month here, with 278 flights.
Across the week, Wednesday is the strongest day at 85.0% on time and Sunday the weakest at 74.3%, a spread of 11 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 51% of the 49,000 delay minutes carriers reported here, and the remaining four split what is left.
- 51%Late-arriving aircraft
- 38%Carrier
- 8%National Airspace System
- 2%Extreme weather
- 0%Security
51% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 49,000 reported delay minutes here, that single category outweighs weather by 22 to one. The split is drawn from 49,432 reported delay minutes.
The largest share of delay minutes, 38%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 19,000 of the 49,000 delay minutes reported here.
Cancellations sit at 0.94% against a national 1.89%, which is ordinary. Diversions add another 0.19%.
Connections and stage length
What a delay here actually costs
8.7% 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 an hour and a half, which a normal layover absorbs.
The 1,045 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
The return leg runs 76.3% on time across 2,645 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 2,650 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 MIA 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 87.4% on time and January 72.5%, a swing of 15 points. If the dates move at all, move them out of January before you think about anything else. 2,620 completed flights over 12 months sit behind that.
Common questions
SJU to MIA questions
How often is SJU to MIA delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.1% of the 2,650 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on SJU to MIA?
Frontier Airlines leads at 79.9% on time across 381 flights. American Airlines is at the other end on 79.0%, a gap of about a point. 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 SJU to MIA?
The 5am–8am departure window is the strongest at 93.5% on time. The 5pm–8pm window is the weakest at 67.7%, 26 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 January delays on SJU to MIA?
January is the weakest month at 72.5% on time, compared with 87.4% in June. Across the year that is 15 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
- MIA to SJU — the return legseparate record
- Luis Munoz Marin International (SJU) delay statistics
- Miami International (MIA) delay statistics
- Frontier Airlines on SJU to MIA79.9%
- American Airlines on SJU to MIA79.0%
- Spirit Airlines on SJU to MIA73.4%
- SJU to MCO, a related route78.0%
- ATL to MIA, a related route71.2%
- SJU to JFK, a related route77.8%
- Frontier Airlines on-time record79.9%
- American Airlines on-time record79.0%
- Spirit Airlines on-time record73.4%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. SJU to MIA and MIA to SJU 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.