Carrier route record

F9ATL→STL

Frontier Airlines · Atlanta to St. Louis

Flights: 205
Period: July 2025 to June 2026
Share of route: 6%
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 STL sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 205 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,371 at 84.7% on time.

The national on-time rate over the same period is 77.6%, so Frontier on ATL to STL runs 8 points behind the country as a whole. Across a thousand flights that is about 79 extra late arrivals.

On time

69.7%

Arrivals under 15 minutes late, of 201 completed flights

Avg delay

57 min

Across delayed arrivals only, not all flights

Cancelled

1.95%

National rate is 1.81%

Whole route

82.4%

Every carrier on ATL to STL, 3,706 flights

These figures cover 205 flights between July 2025 and June 2026. Beyond the headline rate, 10.0% 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 STL

Frontier flew 205 of the 3,706 flights on ATL to STL, about 6% of it. Its 69.7% on time is 13 points worse than the route as a whole, which runs 82.4%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from Delta at 84.7% to Frontier at 69.7%.

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 ATL to STL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	2,371	84.7%	55 min	1.98%	B
Southwest Airlines	1,130	79.9%	56 min	0.53%	B+
Frontier Airlines (this page)thin sample	205	69.7%	57 min	1.95%	C

No carrier stands out. Delta tops the table at 84.7%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.

Departure window

When Frontier runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 26 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am41 flights87.8%
8am–11am79 flights64.9%
11am–2pm37 flights62.2%
2pm–5pm47 flights66.7%
5pm–8pm—
8pm–5am1 flights—

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

The weak window here is the middle of the day, not the evening: 11am–2pm runs 62.2% on time against 87.8% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 8am–11am window is the busiest, with 79 flights scheduled in it.

Across the year

Frontier on ATL to STL through the year

Jul–Sep 202539 flights71.8%
Oct–Dec 202541 flights67.5%
Jan–Mar 202646 flights69.6%
Apr–Jun 202679 flights69.7%

Scale runs 60% 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 69.7% on time across 205 flights.

Quarter by quarter Frontier on ATL to STL held fairly steady: 71.8% in Jul–Sep 2025, 67.5% in Oct–Dec 2025, 69.6% in Jan–Mar 2026 and 69.7% in Apr–Jun 2026. A spread of 4 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Across the week, Thursday is the strongest day at 72.5% on time and Sunday the weakest at 60.5%. 12 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 51% of the 3,481 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
51%
Carrier
40%
National Airspace System
9%

51% 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 3,481 reported delay minutes here, that single category outweighs weather by 51 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 3,481 reported delay minutes.

The largest share of delay minutes, 40%, 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 1,398 of the 3,481 delay minutes reported here.

Cancellations sit at 1.95% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

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. 10.0% 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 484 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.

The return leg is a different operation and performs like one: it runs 62.8% on time across 204 flights, 7 points below 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 7 points of difference.

One caution: this is a thin sample. 205 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 STL

Put together: treat all of this as provisional. 205 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 69.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 201 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