Carrier route record

F9ATL→SJU

Frontier Airlines · Atlanta to San Juan

Flights: 369
Period: July 2025 to June 2026
Share of route: 17%
Carriers: 3

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

Frontier on ATL to SJU earns an F, which is as low as this site's scale goes for a reason. Only 54.7% of flights arrive inside the 15-minute window, 23 points worse than the national rate of 77.6%. Late arrivals average a little over an hour. Treat any tight connection here as a coin flip. That rests on 369 flights, with a median arrival 11 minutes late.

The national on-time rate over the same period is 77.6%, so Frontier on ATL to SJU runs 23 points behind the country as a whole. Across a thousand flights that is about 229 extra late arrivals.

On time

54.7%

Arrivals under 15 minutes late, of 360 completed flights

Avg delay

75 min

Across delayed arrivals only, not all flights

Cancelled

1.63%

National rate is 1.81%

Whole route

70.5%

Every carrier on ATL to SJU, 2,130 flights

These figures cover 369 flights between July 2025 and June 2026. Beyond the headline rate, 17.2% 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

Frontier against every carrier on ATL to SJU

Frontier flew 369 of the 2,130 flights on ATL to SJU, about 17% of it. Its 54.7% on time is 16 points worse than the route as a whole, which runs 70.5%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from Delta at 75.8% to Spirit at 46.2%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on ATL to SJU
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,636	75.8%	51 min	0.92%	B+
Frontier Airlines (this page)	369	54.7%	75 min	1.63%	F
Spirit Airlinesthin sample	125	46.2%	56 min	4.80%	F−

Flight by flight

Frontier flight numbers on ATL to SJU

F9 208210:2555.5% · 297 flights

Departure window

When Frontier runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 369 flights.

5am–8am11 flights—
8am–11am284 flights57.0%
11am–2pm16 flights—
2pm–5pm3 flights—
5pm–8pm16 flights—
8pm–5am39 flights50.0%

Scale runs 40% to 60%. Rows with fewer than 30 flights show a dash.

The early departures do better, though not dramatically: 57.0% on time for the 8am–11am window against 50.0% for 8pm–5am. Worth taking if the schedule allows, not worth an extra connection. The 8am–11am window is the busiest, with 284 flights scheduled in it.

Across the year

Frontier on ATL to SJU through the year

Jul–Sep 202565 flights53.8%
Oct–Dec 202597 flights54.3%
Jan–Mar 2026111 flights52.3%
Apr–Jun 202696 flights58.3%

Scale runs 45% to 65%. 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 54.7% on time across 369 flights.

Quarter by quarter Frontier on ATL to SJU held fairly steady: 53.8% in Jul–Sep 2025, 54.3% in Oct–Dec 2025, 52.3% in Jan–Mar 2026 and 58.3% in Apr–Jun 2026. A spread of 6 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Across the week, Wednesday is the strongest day at 78.1% on time and Saturday the weakest at 33.8%. 44 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Frontier runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 46% of the 12,000 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.

Late-arriving aircraft
46%
Carrier
36%
National Airspace System
18%
Extreme weather
0%

46% 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 12,000 reported delay minutes here, that single category outweighs weather by 46 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 12,278 reported delay minutes.

The largest share of delay minutes, 36%, 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 4,445 of the 12,000 delay minutes reported here.

Cancellations sit at 1.63% against a national 1.81%, which is ordinary. Diversions add another 0.81%.

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. 17.2% 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.

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 runs 56.9% on time across 365 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 369 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 Frontier on ATL to SJU

Put together: treat all of this as provisional. 369 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 54.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 360 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