Carrier route record

NKMIA→SJU

Spirit Airlines · Miami to San Juan

Flights: 179
Period: July 2025 to June 2026
Share of route: 7%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Spirit Airlines.

Spirit on MIA to SJU earns a D−, which is as low as this site's scale goes for a reason. Only 55.8% of flights arrive inside the 15-minute window, 22 points worse than the national rate of 77.6%. Late arrivals average an hour and a half. Treat any tight connection here as a coin flip. That rests on 179 flights. The strongest carrier on the route with a full sample, American Airlines, flew 2,078 at 76.8% on time.

The national on-time rate over the same period is 77.6%, so Spirit on MIA to SJU runs 22 points behind the country as a whole. Across a thousand flights that is about 218 extra late arrivals.

On time

55.8%

Arrivals under 15 minutes late, of 172 completed flights

Avg delay

96 min

Across delayed arrivals only, not all flights

Cancelled

3.91%

National rate is 1.81%

Whole route

74.7%

Every carrier on MIA to SJU, 2,636 flights

These figures cover 179 flights between July 2025 and June 2026. Beyond the headline rate, 23.3% 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

Spirit against every carrier on MIA to SJU

Spirit flew 179 of the 2,636 flights on MIA to SJU, about 7% of it. Its 55.8% on time is 19 points worse than the route as a whole, which runs 74.7%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from American at 76.8% to Spirit at 55.8%.

The two carriers here are closely matched: 5 points 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.

On-time performance by carrier on MIA to SJU
Airline	Flights	On time	Avg delay	Cancelled	Grade
American Airlines	2,078	76.8%	71 min	0.53%	B+
Frontier Airlines	379	71.5%	85 min	1.85%	C
Spirit Airlines (this page)thin sample	179	55.8%	96 min	3.91%	D−

No carrier stands out. American tops the table at 76.8%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.

Departure window

When Spirit runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 34 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am15 flights—
8am–11am35 flights40.0%
11am–2pm7 flights—
2pm–5pm67 flights67.2%
5pm–8pm12 flights—
8pm–5am43 flights33.3%

Scale runs 25% to 75%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 33.3% on time, against 67.2% for the 2pm–5pm 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 2pm–5pm window is the busiest, with 67 flights scheduled in it.

Across the year

Spirit on MIA to SJU through the year

Jul–Sep 202556 flights55.4%
Oct–Dec 202535 flights70.6%
Jan–Mar 202665 flights55.0%
Apr–Jun 202623 flights—

Scale runs 45% to 75%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 55.8% on time across 179 flights.

Spirit on MIA to SJU did not run the same all year. Its best quarter was Oct–Dec 2025 at 70.6% on time and its weakest Jan–Mar 2026 at 55.0%, a swing of 16 points on roughly 60 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Delay causes

Why Spirit runs late on this route

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 7,289 reported delay minutes.

Late-arriving aircraft
39%
National Airspace System
31%
Carrier
28%
Extreme weather
2%

39% 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 7,289 reported delay minutes here, that single category outweighs weather by 25 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 7,289 reported delay minutes.

Cancellations run at 3.91%, against 1.81% nationally. That is about one flight in 25 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 23.3% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 71.1% on time across 184 flights, 15 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 15 points of difference.

One caution: this is a thin sample. 179 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Spirit on MIA to SJU

Put together: the delay figures matter less here than the 3.91% cancellation rate. A late arrival costs you an hour and a half; a cancelled flight costs you the day. Book the 2pm–5pm departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 172 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures