Carrier performance at one airport
WN→STL
Southwest Airlines at St. Louis Lambert International
- Departures
- 39,220
- Period
- September 2025 to August 2026
- Routes
- 25
- Rank here
- #6 of 10
Southwest Airlines at St. Louis sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, about a point worse than the national rate of 77.3%. The late ones land about 55 minutes behind schedule. That rests on 39,220 flights, of which Delta Air Lines flew 5,339 at 88.0% on time.
Measured against the airport rather than the country, Southwest Airlines runs 2 points behind the 77.4% weighted average across all carriers at STL. That is the comparison worth making: every operator here works the same runways, the same airspace and the same weather.
Key figures
On time
75.9%
38,831 completed departures
Avg delay
55 min
Across delayed flights only
Cancelled
0.62%
At STL, this carrier only
Rank here
#6
Of 10 carriers clearing the floor at STL
These figures cover 39,000 flights between September 2025 and August 2026. The median arrival is 3 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.
Against the competition
Every carrier at STL, ranked
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 88.0% of the time; SkyWest Airlines manages 70.0%. Sample sizes sit next to every figure, because a two-point gap across 2,200 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 5,339 | 88.0% | 91 min | 1.55% | A |
| Alaska Airlines | 892 | 83.0% | 49 min | 1.12% | B |
| American Airlines | 5,814 | 82.1% | 122 min | 2.10% | B |
| Republic Airways | 3,131 | 78.9% | 87 min | 4.95% | B− |
| Envoy Air | 1,609 | 76.8% | 86 min | 2.73% | B |
| Southwest Airlines (this page) | 39,220 | 75.9% | 55 min | 0.62% | B+ |
| United Airlines | 2,436 | 75.3% | 81 min | 1.15% | B |
| PSA Airlines | 976 | 75.0% | 117 min | 6.05% | B− |
| Frontier Airlines | 1,433 | 71.9% | 97 min | 2.09% | C |
| SkyWest Airlines | 2,200 | 70.0% | 100 min | 2.55% | C |
PSA Airlines cancels 6.0% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Route by route
Where Southwest Airlines flies from STL
Southwest Airlines operates 25 routes out of STL with enough volume to report. Route records inside one carrier at one airport still spread widely, because a short shuttle and a transcontinental have very different exposure to a late inbound.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| STL to DEN · Denver | 2,190 | 72.6% | 60 min | 0.09% | C+ |
| STL to MCO · Orlando | 2,143 | 78.4% | 59 min | 0.61% | B+ |
| STL to DAL · Dallas | 1,944 | 75.2% | 60 min | 1.39% | B |
| STL to LAS · Las Vegas | 1,789 | 74.7% | 53 min | 0.22% | C+ |
| STL to MDW · Chicago | 1,698 | 79.5% | 52 min | 1.18% | B |
| STL to PHX · Phoenix | 1,619 | 71.3% | 52 min | 0.31% | C+ |
| STL to HOU · Houston | 1,547 | 78.2% | 55 min | 0.26% | B+ |
| STL to DCA · Washington | 1,404 | 72.7% | 57 min | 1.50% | C |
| STL to LGA · New York | 1,395 | 69.2% | 57 min | 3.08% | C− |
| STL to BNA · Nashville | 1,282 | 81.2% | 52 min | 0.62% | B+ |
| STL to BWI · Baltimore | 1,271 | 79.3% | 59 min | 1.26% | B |
| STL to TPA · Tampa | 1,205 | 80.4% | 60 min | 0.41% | B+ |
| STL to ATL · Atlanta | 1,091 | 79.2% | 54 min | 1.10% | B |
| STL to MCI · Kansas City | 1,017 | 75.5% | 53 min | 0.20% | B+ |
| STL to RSW · Fort Myers | 1,009 | 78.7% | 53 min | 0.40% | B+ |
| STL to AUS · Austin | 972 | 75.2% | 54 min | 0.31% | B+ |
| STL to BOS · Boston | 938 | 62.8% | 59 min | 0.75% | D+ |
| STL to OMA · Omaha | 811 | 75.9% | 54 min | 0.12% | B+ |
| STL to FLL · Fort Lauderdale | 775 | 74.5% | 51 min | 0.65% | C+ |
| STL to MSY · New Orleans | 734 | 82.8% | 58 min | 0.14% | B+ |
| STL to PHL · Philadelphia | 725 | 72.6% | 58 min | 0.41% | C+ |
| STL to CLE · Cleveland | 691 | 81.0% | 51 min | 0.29% | B+ |
| STL to MKE · Milwaukee | 686 | 81.5% | 59 min | 0.58% | B+ |
| STL to LAX · Los Angeles | 674 | 71.6% | 48 min | 0.15% | C+ |
| STL to CMH · Columbus | 668 | 80.2% | 52 min | 0.30% | B+ |
Departure window
Best time of day for this operation
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 29 points, against 18 points between the best and worst carrier.
- 5am–8am4,456 flights92.9%
- 8am–11am10,990 flights87.5%
- 11am–2pm4,338 flights77.4%
- 2pm–5pm6,288 flights66.7%
- 5pm–8pm6,484 flights65.1%
- 8pm–5am6,664 flights63.5%
Scale runs 55% to 100%.
The 8pm–5am window is where this operation falls apart: 63.5% on time, against 92.9% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8am–11am window is the busiest, with 10,990 flights scheduled in it.
Across the year
Seasonal pattern
June is the worst month at 64.2% on time, 21 points below February, the best at 84.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. October was the busiest month here, with 3,567 flights.
Delay causes
What holds this operation up
- 52%Late-arriving aircraft
- 26%Carrier
- 19%National Airspace System
- 3%Extreme weather
- 0%Security
52% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 511,000 reported delay minutes here, that single category outweighs weather by 17 to one. The split is drawn from 510,988 reported delay minutes.
Cancellations are rare at 0.62%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
7.0% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about 55 minutes, which a normal layover absorbs.
39,220 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 84.9% on time and June 64.2%, a swing of 21 points. If the dates move at all, move them out of June before you think about anything else. 38,831 completed flights over 12 months sit behind that.
Common questions
Southwest Airlines at STL
How often is Southwest Airlines at STL delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 24.1% of the 39,220 flights in this analysis, against 22.7% nationally. Delayed flights are late by about 55 minutes on average.
Which airline is most reliable on Southwest Airlines at STL?
Delta Air Lines leads at 88.0% on time across 5,339 flights. SkyWest Airlines is at the other end on 70.0%, a gap of 18 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on Southwest Airlines at STL?
The 5am–8am departure window is the strongest at 92.9% on time. The 8pm–5am window is the weakest at 63.5%, 29 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are June delays on Southwest Airlines at STL?
June is the weakest month at 64.2% on time, compared with 84.9% in February. Across the year that is 21 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- Southwest Airlines network-wide record
- St. Louis Lambert International (STL) all carriers
- STL to DEN route record72.6%
- STL to MCO route record78.4%
- STL to DAL route record75.2%
- STL to LAS route record74.7%
- Why the first flight of the morning is statistically safest
- Do airlines run better at their own hubs?
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.