Best time to fly out of St. Louis Lambert (STL)
The early-flight folk wisdom holds up at St. Louis Lambert: departures in the Before 6am band left on time 94% of the time, against 54.6% in the 10pm–12am band. These are historical odds, not forecasts. The records say what happened on this schedule over three years; they know nothing about tomorrow’s thunderstorm.
Data through June 2026 · Bureau of Transportation Statistics
On-time rate by hour and day
On this page, “on time” means a departure that pushed back less than 15 minutes behind its scheduled time — the Bureau of Transportation Statistics definition, and the one airlines are held to.
| Departure time | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|---|
| Before 6am | 93 | 95 | 95 | 97 | 94 | 92 | 92 |
| 6–8am | 89 | 92 | 93 | 92 | 92 | 90 | 90 |
| 8–10am | 83 | 88 | 89 | 89 | 87 | 86 | 87 |
| 10am–12pm | 81 | 87 | 88 | 84 | 83 | 84 | 84 |
| 12–2pm | 74 | 83 | 84 | 79 | 78 | 76 | 75 |
| 2–4pm | 72 | 78 | 77 | 71 | 71 | 72 | 68 |
| 4–6pm | 69 | 74 | 70 | 64 | 65 | 70 | 62 |
| 6–8pm | 68 | 73 | 71 | 62 | 66 | 65 | 59 |
| 8–10pm | 65 | 71 | 68 | 56 | 65 | 50 | 56 |
| 10pm–12am | 56 | 56 | 53 | 59 | 56 | 54 | 50 |
The steadiest stretch at STL was Before 6am — 94% of departures left on time across 8,968 flights. The weakest was 10pm–12am at 54.6%. 6–8am departures from STL left on time 91.2% of the time across 27,541 flights; 6–8pm departures, 66.4% across 23,125. That is a gap of 24.8 points, and it is the whole case for the early flight.
The year at STL
July was the hard month at STL: 67.5% of departures left on time, across 17,379 flights. September was the easy one at 83.5%. Each month pools three years of that month, so a single bad week does not decide it.
| Month | Share departures that left on time | Flights |
|---|---|---|
| January | 79.3% | 14,335 |
| February | 83.2% | 13,506 |
| March | 76.5% | 16,230 |
| April | 79.9% | 16,039 |
| May | 73.8% | 16,659 |
| June | 71.1% | 17,021 |
| July | 67.5% | 17,379 |
| August | 78.2% | 16,794 |
| September | 83.5% | 16,163 |
| October | 81.8% | 17,076 |
| November | 82.9% | 15,710 |
| December | 75.9% | 16,013 |
Airlines at STL
Every airline with at least 100 departures from STL, busiest first. These are that airline’s departures from this airport only — its record across the country sits on its own page.
| Airline | Left on time | Typical delay | Cancelled | Departures |
|---|---|---|---|---|
| Southwest Airlines | 75% | 50 min | 0.8% | 121,821 |
| American Airlines | 81% | 118 min | 1.7% | 19,016 |
| Delta Air Lines | 88.3% | 91 min | 1% | 16,373 |
| United Airlines | 78.4% | 85 min | 1.2% | 8,170 |
| Republic Airways | 86.3% | 85 min | 3.4% | 7,740 |
| Envoy Air | 79% | 73 min | 2% | 5,089 |
| SkyWest Airlines | 75.4% | 104 min | 2% | 3,785 |
| Frontier Airlines | 73.9% | 99 min | 2.3% | 3,585 |
| Alaska Airlines | 83.1% | 54 min | 1% | 2,397 |
| Endeavor Air | 87% | 77 min | 3.6% | 2,158 |
| PSA Airlines | 80% | 123 min | 4.8% | 1,924 |
| Spirit Airlines | 66.5% | 84 min | 3.1% | 867 |
Spirit Airlines (through May 2026) and Endeavor Air (through December 2024) stopped filing before June 2026. Their rows cover a shorter run of months than the rest of the table, so their figures are not set against the others anywhere on this page.
What delays out of STL were put down to
Airlines file a reason with every arrival running 15 minutes late or more. Across 39,388 flights that departed STL and ran 15 minutes late or more, the delay minutes break down with 45.7% put down to late-arriving aircraft and 31% to airline operations.
- Late-arriving aircraft 45.7%
- Airline operations 31%
- Air traffic & airport volume 19.2%
- Severe weather 4%
- Security 0.2%
Late-arriving aircraft is the knock-on category: the plane came in late, so it went out late again. It is why a 7am problem in Newark is still a problem in Denver at dinnertime, and why it is usually the biggest slice on the bar.
If you are connecting through STL
Of 192,931 scheduled arrivals into STL, 79.1% reached the gate less than 15 minutes behind schedule. Of the 37,804 arrivals that ran late, 57.4% were no more than 45 minutes behind — which is the difference between a tight connection and a new boarding pass.
Work out a specific layover — pick the airport and the minutes you have, and the tool reads the same arrival records back as a share.
Busiest routes out of STL
Ranked by flights, with the share that arrived on time at the far end. Where a route carries enough flights for a page of its own the chip goes there; otherwise it goes to the destination airport.
- DEN 77.2% on time · 11,538 flights
- ATL 85.3% on time · 10,709 flights
- LGA 80.9% on time · 9,725 flights
- ORD 75.4% on time · 8,222 flights
- MCO 78.5% on time · 7,388 flights
- DCA 76.7% on time · 6,993 flights
- DFW 74.9% on time · 6,938 flights
- PHX 78.1% on time · 6,748 flights
- LAS 78.3% on time · 6,232 flights
- DAL 78.6% on time · 6,122 flights
STL in one number
St. Louis Lambert (STL)
Rank 31 of 363 US airports by departures. Steadiest stretch of the day: Before 6am. Hardest month: July.
Questions about STL
- What is the best time of day to fly out of St. Louis Lambert?
- Before 6am. Departures in that band left on time 94% of the time across 8,968 flights, July 2023 through June 2026 — the best of the ten bands in the day. The 10pm–12am band was the weakest at 54.6%.
- Is the early flight out of STL really more reliable?
- 6–8am departures from STL left on time 91.2% of the time across 27,541 flights; 6–8pm departures, 66.4% across 23,125. That is a gap of 24.8 points, and it is the whole case for the early flight.
- What is the worst month to fly out of STL?
- July: 67.5% of the departures that flew left on time, with 17,379 scheduled. September was the other end of the year at 83.5%. Each figure pools three years of that calendar month.
- Which airline is most on time at STL?
- Delta Air Lines — 88.3% of its 16,373 departures from STL left on time. Frontier Airlines sat at the other end at 73.9% over 3,585 flights. Only airlines with at least 100 departures here are ranked. Airlines that stopped filing before June 2026 are left out of the ranking — their figures cover a shorter run of months than the rest of the table.
- How often are flights cancelled at STL?
- 1.2% of scheduled departures were cancelled over July 2023 through June 2026. Cancellations are counted against everything scheduled, not against everything that flew — a rate that looks small still adds up to real people in a rebooking line.