Carrier route record

DLSTL→ATL

Delta Air Lines · St. Louis to Atlanta

Flights: 2,371
Period: July 2025 to June 2026
Share of route: 64%
Carriers: 3

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

Delta on STL to ATL earns an A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 12 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 2,371 flights, with a median arrival 15 minutes early.

Set against the rest of the country, Delta's STL to ATL record is 12 points better than the US average of 77.6%. That gap is worth roughly 118 fewer late arrivals for every thousand flights.

On time

89.4%

Arrivals under 15 minutes late, of 2,319 completed flights

Avg delay

77 min

Across delayed arrivals only, not all flights

Cancelled

1.98%

National rate is 1.81%

Whole route

85.3%

Every carrier on STL to ATL, 3,705 flights

These figures cover 2,371 flights between July 2025 and June 2026. The median arrival is 15 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Delta against every carrier on STL to ATL

Delta flew 2,371 of the 3,705 flights on STL to ATL, most of the route. Its 89.4% on time is 4 points better than the route as a whole, which runs 85.3%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from Delta at 89.4% to Frontier at 62.8%. 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 STL to ATL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)	2,371	89.4%	77 min	1.98%	A
Southwest Airlines	1,130	80.7%	59 min	1.15%	B
Frontier Airlinesthin sample	204	62.8%	92 min	1.96%	D

Flight by flight

Delta flight numbers on STL to ATL

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 10 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am722 flights93.8%
8am–11am412 flights93.8%
11am–2pm472 flights87.5%
2pm–5pm278 flights84.6%
5pm–8pm487 flights83.7%
8pm–5am—

Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 93.8% of the time, against 83.7% for the evening window. That is 10 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 722 flights scheduled in it.

Across the year

Delta on STL to ATL through the year

Darker means more delays. Figures are on-time percentages.September best, December worst

December is the weak month at 83.4% on time, against 96.7% in September. 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. July was the busiest month here, with 224 flights.

Across the week, Wednesday is the strongest day at 95.1% on time and Monday the weakest at 85.1%. 10 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 43% of the 19,000 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.

Carrier
43%
Late-arriving aircraft
35%
National Airspace System
17%
Extreme weather
5%

35% 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 19,000 reported delay minutes here, that single category outweighs weather by 7 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 18,839 reported delay minutes.

The largest share of delay minutes, 43%, 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 8,054 of the 19,000 delay minutes reported here.

Cancellations sit at 1.98% against a national 1.81%, which is ordinary. Diversions add another 0.21%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 3.9% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

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 84.7% on time across 2,371 flights, 5 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 5 points of difference.

The sample behind these figures is 2,371 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.

What to do with this

Booking Delta on STL to ATL

Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 96.7% on time and December 83.4%, a swing of 13 points. If the dates move at all, move them out of December before you think about anything else. 2,319 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