Airport month record
STLAUG
St. Louis Lambert International in August 2025
- Departures
- 5,539
- Month
- August 2025
- National, same month
- 77.4%
- Carriers
- 10
Historical statistics for August 2025, not live status or a forecast for this year’s August. For today’s conditions at STL, see live FAA status.
STL in August lands a B+, 2 points better than the national rate of 77.4%. About one flight in five arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 5,539 flights, of which Delta Air Lines flew 494 at 90.2% on time.
Delta Air Lines is the most reliable of the three carriers covered here at 90.2% on time across 494 flights.
Key figures
On time
79.7%
Arrivals under 15 minutes late, of 5,470 completed departures
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
0.96%
Nationally in August: 1.08%
Whole year
78.0%
STL across all twelve months
These figures cover 5,539 departures from St. Louis Lambert International in August 2025. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.
Against the year
August next to STL's other months
Against STL's own year, August ran 2 points better than the twelve-month rate of 78.0%, which makes it number six of twelve months, best first. Either side of it, July ran 71.7% on time and September 83.8%, so this month sits in line with its neighbours.
| Month | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| July 2025 | 5,855 | 71.7% | 73 min | 1.57% | C |
| August 2025 (this page) | 5,539 | 79.7% | 71 min | 0.96% | B+ |
| September 2025 | 5,321 | 83.8% | 58 min | 0.34% | B+ |
| October 2025 | 5,611 | 78.5% | 60 min | 0.27% | B+ |
| November 2025 | 5,202 | 80.1% | 76 min | 1.46% | B |
| December 2025 | 5,359 | 74.0% | 75 min | 0.90% | C+ |
| January 2026 | 4,683 | 83.1% | 74 min | 3.46% | B− |
| February 2026 | 4,484 | 84.9% | 64 min | 1.32% | B |
| March 2026 | 5,400 | 75.3% | 74 min | 2.52% | B |
| April 2026 | 5,156 | 80.8% | 65 min | 0.80% | B+ |
| May 2026 | 5,375 | 77.5% | 74 min | 0.84% | B+ |
| June 2026 | 5,463 | 69.0% | 68 min | 1.17% | C |
Departure window
The best time of day to leave STL in August
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 25 points, against 13 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am984 flights91.6%
- 8am–11am1,373 flights89.6%
- 11am–2pm681 flights79.7%
- 2pm–5pm902 flights73.9%
- 5pm–8pm1,057 flights67.2%
- 8pm–5am542 flights66.8%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.6% of the time, against 66.8% for the overnight window. That is 25 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 1,373 flights scheduled in it.
Across the week, Tuesday is the strongest day at 87.7% on time and Sunday the weakest at 74.2%. 14 points is a smaller lever than departure hour, but it is free.
Carrier by carrier
Which airlines ran best at STL in August
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 90.2% of the time; American Airlines manages 77.2%. Sample sizes sit next to every figure, because a two-point gap across 552 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 3,488 | 79.9% | 56 min | 0.69% | B+ |
| American Airlines | 552 | 77.2% | 114 min | 1.09% | B |
| Delta Air Lines | 494 | 90.2% | 68 min | 1.01% | A |
| SkyWest Airlinesthin sample | 226 | 69.7% | 91 min | 1.77% | C |
| Republic Airwaysthin sample | 225 | 84.5% | 76 min | 2.67% | B |
| United Airlinesthin sample | 199 | 69.9% | 91 min | 2.01% | C |
| Envoy Airthin sample | 119 | 84.6% | 84 min | 1.68% | B |
| Alaska Airlinesthin sample | 88 | 70.1% | 41 min | 0.00% | C+ |
| Frontier Airlinesthin sample | 87 | 69.4% | 144 min | 2.30% | C |
| Spirit Airlinesthin sample | 34 | 79.4% | 162 min | 0.00% | B+ |
The spread between Delta and American is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.
Route by route
Busiest routes out of STL in August
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| STL to ATL · Atlantathin sample | 331 | 87.1% | 66 min | 1.51% | A |
| STL to DEN · Denverthin sample | 330 | 70.6% | 86 min | 0.00% | C+ |
| STL to ORD · Chicagothin sample | 255 | 69.0% | 85 min | 3.92% | C− |
| STL to LGA · New Yorkthin sample | 240 | 81.4% | 63 min | 1.67% | B |
| STL to DFW · Dallas-Fort Worththin sample | 203 | 72.1% | 100 min | 2.46% | C |
| STL to DCA · Washingtonthin sample | 197 | 72.7% | 59 min | 1.02% | C |
| STL to MCO · Orlandothin sample | 184 | 75.0% | 61 min | 1.09% | B |
| STL to DTW · Detroitthin sample | 175 | 85.7% | 81 min | 0.00% | A+ |
| STL to DAL · Dallasthin sample | 173 | 76.3% | 76 min | 1.16% | B |
| STL to PHX · Phoenixthin sample | 165 | 74.5% | 99 min | 0.00% | C+ |
| STL to CLT · Charlottethin sample | 162 | 83.2% | 117 min | 0.62% | B+ |
| STL to LAS · Las Vegasthin sample | 159 | 84.1% | 137 min | 1.26% | B |
| STL to MSP · Minneapolisthin sample | 159 | 85.4% | 69 min | 0.63% | A+ |
| STL to MDW · Chicagothin sample | 152 | 76.2% | 49 min | 0.66% | B+ |
| STL to BOS · Bostonthin sample | 145 | 84.1% | 61 min | 0.00% | B+ |
| STL to PHL · Philadelphiathin sample | 142 | 79.4% | 87 min | 0.00% | B+ |
| STL to HOU · Houstonthin sample | 130 | 79.7% | 53 min | 0.77% | B+ |
| STL to BWI · Baltimorethin sample | 129 | 85.8% | 50 min | 1.55% | A |
| STL to SEA · Seattlethin sample | 111 | 68.2% | 43 min | 0.00% | C+ |
| STL to BNA · Nashvillethin sample | 109 | 89.9% | 34 min | 0.00% | A+ |
| STL to TPA · Tampathin sample | 94 | 75.3% | 52 min | 0.00% | B+ |
| STL to EWR · Newarkthin sample | 93 | 79.1% | 92 min | 2.15% | B |
| STL to LAX · Los Angelesthin sample | 92 | 83.7% | 55 min | 0.00% | B+ |
| STL to MCI · Kansas Citythin sample | 92 | 76.9% | 41 min | 1.09% | B |
| STL to SLC · Salt Lake Citythin sample | 88 | 88.5% | 77 min | 1.14% | A |
Delay causes
What held STL up in August
One category carries most of the weight here. Late-arriving aircraft accounts for 45% of the 78,000 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.
- 45%Late-arriving aircraft
- 31%Carrier
- 19%National Airspace System
- 5%Extreme weather
- 0%Security
45% 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 78,000 reported delay minutes here, that single category outweighs weather by 8 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 78,217 reported delay minutes.
Cancellations sit at 0.96% against a national 1.08%, which is ordinary. Diversions add another 0.29%.
6.8% of arrivals land an hour or more late, close to the national 8.2%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.
What to do with this
Flying from STL in August
For a August trip through STL: expect 79.7% on time and 0.96% cancelled, going by August 2025. The 5am–8am window was the strongest part of the day.
Related
Where to go next
- St. Louis Lambert International (STL), the whole year
- STL in July71.7%
- STL in September83.8%
- STL in October78.5%
- STL in November80.1%
- STL in December74.0%
- STL in January83.1%
- STL in February84.9%
- STL in March75.3%
- STL in April80.8%
- STL in May77.5%
- STL in June69.0%
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.