St. Louis, MO · departure reliability
STL
St. Louis Lambert International
- Departures
- 63,096
- Period
- September 2025 to August 2026
- Carriers
- 10
- US rank
- #32 by volume
St. Louis
St. Louis Lambert International lands a B, level with the national rate of 77.3%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 63,096 flights, of which Delta Air Lines flew 5,339 at 88.0% on time.
Delta Air Lines is the most reliable of the ten carriers covered here at 88.0% on time across 5,339 flights.
Key figures
On time
77.4%
Departures arriving under 15 minutes late at their destination
Avg delay
69 min
Across delayed flights only
Cancelled
1.32%
National rate is 1.89%
Best carrier
Delta
88.0% on time here
These figures cover 63,000 flights between September 2025 and August 2026. The median arrival is 6 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
Which airlines run best out of STL
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 |
|---|---|---|---|---|---|
| Southwest Airlines | 39,220 | 75.9% | 55 min | 0.62% | B+ |
| American Airlines | 5,814 | 82.1% | 122 min | 2.10% | B |
| Delta Air Lines | 5,339 | 88.0% | 91 min | 1.55% | A |
| Republic Airways | 3,131 | 78.9% | 87 min | 4.95% | B− |
| United Airlines | 2,436 | 75.3% | 81 min | 1.15% | B |
| SkyWest Airlines | 2,200 | 70.0% | 100 min | 2.55% | C |
| Envoy Air | 1,609 | 76.8% | 86 min | 2.73% | B |
| Frontier Airlines | 1,433 | 71.9% | 97 min | 2.09% | C |
| PSA Airlines | 976 | 75.0% | 117 min | 6.05% | B− |
| Alaska Airlines | 892 | 83.0% | 49 min | 1.12% | B |
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
Busiest routes out of STL
Route-level records vary far more than the airport average. These are the 25 busiest departures from STL, each with its own on-time rate against the airport-wide 77.4%.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| STL to DEN · Denver | 3,687 | 75.0% | 69 min | 0.33% | B+ |
| STL to ATL · Atlanta | 3,673 | 84.6% | 71 min | 1.63% | B |
| STL to ORD · Chicago | 3,112 | 72.5% | 102 min | 3.50% | C− |
| STL to LGA · New York | 2,578 | 74.0% | 68 min | 3.84% | C− |
| STL to MCO · Orlando | 2,539 | 77.5% | 63 min | 0.91% | B+ |
| STL to DCA · Washington | 2,417 | 73.7% | 74 min | 3.19% | C− |
| STL to DFW · Dallas-Fort Worth | 2,391 | 76.2% | 114 min | 3.05% | B− |
| STL to PHX · Phoenix | 2,309 | 74.8% | 77 min | 0.52% | C+ |
| STL to LAS · Las Vegas | 2,107 | 74.9% | 61 min | 0.62% | C+ |
| STL to MSP · Minneapolis | 1,962 | 79.4% | 75 min | 0.92% | B+ |
| STL to DAL · Dallas | 1,944 | 75.2% | 60 min | 1.39% | B |
| STL to DTW · Detroit | 1,899 | 81.1% | 85 min | 1.21% | B |
| STL to CLT · Charlotte | 1,823 | 83.7% | 94 min | 1.37% | B |
| STL to MDW · Chicago | 1,698 | 79.5% | 52 min | 1.18% | B |
| STL to BOS · Boston | 1,616 | 66.9% | 69 min | 1.79% | C |
| STL to PHL · Philadelphia | 1,606 | 78.7% | 88 min | 1.81% | B |
| STL to HOU · Houston | 1,547 | 78.2% | 55 min | 0.26% | B+ |
| 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 | 1,234 | 80.1% | 60 min | 0.57% | B+ |
| STL to MIA · Miami | 1,200 | 81.9% | 62 min | 0.67% | B+ |
| STL to EWR · Newark | 1,075 | 81.4% | 92 min | 5.49% | B− |
| STL to LAX · Los Angeles | 1,028 | 72.7% | 58 min | 0.39% | C+ |
| 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+ |
Departure window
The best time of day to leave STL
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 26 points, against 18 points between the best and worst carrier.
- 5am–8am11,133 flights90.1%
- 8am–11am14,957 flights86.8%
- 11am–2pm7,867 flights77.7%
- 2pm–5pm10,486 flights70.1%
- 5pm–8pm11,127 flights67.8%
- 8pm–5am7,526 flights64.1%
Scale runs 55% to 95%.
The 8pm–5am window is where this operation falls apart: 64.1% on time, against 90.1% 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 14,957 flights scheduled in it.
Explore
Filter STL departures by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On departures from St. Louis (STL), the best departure window is 5am–8am at 90.1% on time and the worst is 8pm–5am at 64.1%, a wide gap of 26.0 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am90.1%
- 8–11am86.8%
- 11am–2pm77.7%
- 2–5pm70.1%
- 5–8pm67.8%
- 8pm–5am64.1%
best all US flightsScale 55% to 95%.
Across the year
When STL runs late
STL's year swings by 16 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
June is the worst month at 69.0% on time, 16 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. July was the busiest month here, with 5,725 flights.
Across the week, Wednesday is the strongest day at 83.0% on time and Sunday the weakest at 72.5%, a spread of 11 points.
STL month by month
From Europe
Transatlantic routes into STL
1 European airport sends scheduled passenger flights to STL, 302 flights a year in both directions by the DOT's international count. The DOT keeps no delay record for international flights; the UK routes carry the CAA's departure punctuality, and every route sets its departure airport's EUROCONTROL figures beside STL's own record above.
Delay causes
Why STL gets delayed
Late-arriving aircraft accounts for 45% of the 964,000 delay minutes carriers reported here, and the remaining four split what is left.
- 45%Late-arriving aircraft
- 30%Carrier
- 20%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. Across 964,000 reported delay minutes here, that single category outweighs weather by 10 to one. The split is drawn from 963,544 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.1% on time here.
Cancellations sit at 1.32% against a national 1.89%, which is ordinary. Diversions add another 0.32%.
7.7% 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 a little over an hour, which a normal layover absorbs.
63,096 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.
What to do with this
Flying out of STL
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 84.9% on time and June 69.0%, a swing of 16 points. If the dates move at all, move them out of June before you think about anything else. 62,059 completed flights over 12 months sit behind that.
Common questions
STL delay questions
How often is St. Louis (STL) delayed?
Roughly 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 22.6% of the 63,096 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on St. Louis (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 St. Louis (STL)?
The 5am–8am departure window is the strongest at 90.1% on time. The 8pm–5am window is the weakest at 64.1%, 26 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 St. Louis (STL)?
June is the weakest month at 69.0% on time, compared with 84.9% in February. Across the year that is 16 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
- STL to DEN — Denver75.0%
- STL to ATL — Atlanta84.6%
- STL to ORD — Chicago72.5%
- STL to LGA — New York74.0%
- STL to MCO — Orlando77.5%
- STL to DCA — Washington73.7%
- Southwest Airlines on-time record75.9%
- American Airlines on-time record82.1%
- Delta Air Lines on-time record88.0%
- Republic Airways on-time record78.9%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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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.