Carrier route record

F9STL→ATL

Frontier Airlines · St. Louis to Atlanta

Flights: 204
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 STL to ATL draws a D. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is an hour and a half behind schedule. Build slack into anything you connect to. That rests on 204 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,371 at 89.4% on time.

The national on-time rate over the same period is 77.6%, so Frontier on STL to ATL runs 15 points behind the country as a whole. Across a thousand flights that is about 148 extra late arrivals.

On time

62.8%

Arrivals under 15 minutes late, of 199 completed flights

Avg delay

92 min

Across delayed arrivals only, not all flights

Cancelled

1.96%

National rate is 1.81%

Whole route

85.3%

Every carrier on STL to ATL, 3,705 flights

These figures cover 204 flights between July 2025 and June 2026. Beyond the headline rate, 14.1% 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 STL to ATL

Frontier flew 204 of the 3,705 flights on STL to ATL, about 6% of it. Its 62.8% on time is 23 points worse than the route as a whole, which runs 85.3%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from Delta at 89.4% to Frontier at 62.8%.

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 89.4% of the time; Southwest Airlines manages 80.7%. Sample sizes sit next to every figure, because a two-point gap across 1,130 flights means less than a ten-point one.

On-time performance by carrier on STL to ATL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	2,371	89.4%	77 min	1.98%	A
Southwest Airlines	1,130	80.7%	59 min	1.15%	B
Frontier Airlines (this page)thin sample	204	62.8%	92 min	1.96%	D

Delta leads Southwest by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

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 19 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am—
8am–11am11 flights—
11am–2pm41 flights56.4%
2pm–5pm50 flights62.0%
5pm–8pm61 flights59.3%
8pm–5am41 flights75.6%

Scale runs 50% to 80%. 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 56.4% on time against 75.6% for 8pm–5am. 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 5pm–8pm window is the busiest, with 61 flights scheduled in it.

Across the year

Frontier on STL to ATL through the year

Jul–Sep 202539 flights66.7%
Oct–Dec 202540 flights68.4%
Jan–Mar 202646 flights56.5%
Apr–Jun 202679 flights61.8%

Scale runs 50% 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 62.8% on time across 204 flights.

Frontier on STL to ATL did not run the same all year. Its best quarter was Oct–Dec 2025 at 68.4% on time and its weakest Jan–Mar 2026 at 56.5%, a swing of 12 points on roughly 51 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.

Across the week, Thursday is the strongest day at 75.0% on time and Monday the weakest at 43.3%. 32 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 43% of the 6,809 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
43%
Carrier
25%
National Airspace System
17%
Extreme weather
15%

Extreme weather accounts for 15% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.4 times the usual weather exposure. The split is drawn from 6,809 reported delay minutes.

43% 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 6,809 reported delay minutes here, that single category outweighs weather by 3 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.

Cancellations sit at 1.96% against a national 1.81%, which is ordinary. Diversions add another 0.49%.

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. 14.1% 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 8pm–5am window matters as much as it does.

The return leg is a different operation and performs like one: it runs 69.7% on time across 205 flights, 7 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 7 points of difference.

One caution: this is a thin sample. 204 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 STL to ATL

Put together: treat all of this as provisional. 204 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 62.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 199 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