Route profile
STL→DEN
Flight reliability, delays and best times to fly from St. Louis to Denver, 770 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 46% of comparable major US routes (4,598 compared)
Calculated from 11,911 flights. How this is calculated
STL → DEN arrives on time 77.0% of the time; the return trip, DEN → STL, arrives on time 76.4% of the time.
STL → DEN spends 23.0 minutes on the ground on a 770-mile trip: 14.1 minutes from pushback to wheels-up at STL and 9.0 minutes from touchdown to gate at DEN.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
Every day of the week performs about the same on this route, steadier than 94% of 4,467 comparable routes.
79.8% on time on the best day (Tuesday) against 75.5% on the worst (Sunday).
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 4,467 in the comparison.
Why STL → DEN flights are cancelled
July 2023 – July 2026
STL → DEN cancelled 89 of 11,911 scheduled flights — about 1 in every 134. The reason filed most often was extreme weather, 55.1% of the cancellations coded on this route — about 1 in every 243 scheduled flights.
Share of cancellations
Of 89 cancelled departures carrying a reason code.
What each reason means
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
49 cancellations, 55.1% of the total.
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
36 cancellations, 40.4% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
4 cancellations, 4.5% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
89 coded cancellations were recorded on STL → DEN; the section appears from 50.
When it goes wrong
July 2023 – July 2026
49 min late
against a median of 4 min early
Percentiles over 11,911 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at DEN after arriving from STL.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 40% | Likely to miss |
| 45 min | 22% | High risk |
| 60 min | 15% | Some risk |
| 90 min | 8.1% | Some risk |
| 120 min | 5.0% | Some risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 0.75% of the time and diverts 0.23% of the time, which a late arrival never shows up in.
Chance of missing is the share of 11,795 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 49 minutes late (90th-percentile gate arrival delay), over 11,911 operations.
Any other layover length: connection checker.
Best time to fly
STL → DEN flights departing 5–9 AM arrived on time 89.6% of the time, against 61.9% for 3–6 PM departures, a gap of 27.7 percentage points.
By departure window
By departure hour
- 12 AM to 4 AM: too few flights to score
- 5 AM: 92.7% on time from 1,136 flights
- 6 AM: 94.4% on time from 471 flights
- 7 AM: 93.0% on time from 503 flights
- 8 AM: 82.0% on time from 992 flights
- 9 AM: 84.0% on time from 839 flights
- 10 AM: 84.1% on time from 450 flights
- 11 AM: 83.6% on time from 372 flights
- 12 PM: 82.5% on time from 340 flights
- 1 PM: 83.4% on time from 1,538 flights
- 2 PM: 79.9% on time from 454 flights
- 3 PM: 72.9% on time from 445 flights
- 4 PM: 60.6% on time from 1,503 flights
- 5 PM: 56.6% on time from 536 flights
- 6 PM: 60.0% on time from 624 flights
- 7 PM: 63.0% on time from 519 flights
- 8 PM: 75.2% on time from 557 flights
- 9 PM: 68.2% on time from 344 flights
- 10 PM: 62.7% on time from 262 flights
- 11 PM: too few flights to score
Why STL → DEN runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
airspace and airport capacity, including weather-driven flow control
crew, maintenance, boarding and fueling, all within the carrier’s control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for STL → DEN. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on STL → DEN, at 39.3%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 89.6% of the time and 3–6 PM departures 61.9%.
How this route holds up in bad weather
July 2023 – July 2026
Bad weather raises cancellations by a similar amount at both ends of STL to DEN: 3.7 times the normal rate at STL and 4.0 times at DEN. Cancelled in bad weather against normal hours: STL 3.5% against 0.9%, DEN 2.8% against 0.7%. Flights that did leave DEN in bad weather arrived on time 51.5% of the time, against 78.8% in normal hours.
Bad weather and normal hours at the airports
Scheduled departures, July 2023 – July 2026| Departures from | STL | DEN |
|---|---|---|
| Cancelled in bad weather | 3.5% | 2.8% |
| Cancelled in normal hours | 0.9% | 0.7% |
| Arrived on time, bad weather | 67.0% | 51.5% |
| Arrived on time, normal hours | 80.4% | 78.8% |
| Departures in bad weather | 18,612 | 92,610 |
Southwest Airlines (3.2% cancelled against 4.3% for the other carriers at STL) cancelled fewer departures from STL in bad weather than the other carriers there did in the same months. None of the route’s other carriers was clearly worse. 2 more carriers fly this route but has too few bad-weather departures from STL to compare.
This route’s airlines in bad weather at STL
All departures from STL| Airline | Bad-weather departures | Cancelled | Other carriers |
|---|---|---|---|
| Southwest Airlines | 11,665 | 3.2%below the others | 4.3% |
| United Airlines | 801 | 3.5%about level | 3.1% |
These are airport figures, not route figures: every scheduled departure from STL and DEN, to any destination, in hours the weather report called bad. The airline rows count each carrier’s departures from STL on every route.
Weather source and limits. In full: STL (airlines), DEN, What Weather Costs Each Airport, Who Cancels More When the Weather Turns, Airports That Change Places When Weather Turns.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| Southwest Airlines | 7,055 | 76.9% | 0.57% | -4 min | 7.7% |
| United Airlines | 3,528 | 77.6% | 0.91% | -4 min | 9.1% |
| Frontier Airlines | 1,084 | 73.7% | 1.48% | -5 min | 10.8% |
| SkyWest Airlines | 244 | 88.8% | 0.41% | -12 min | 3.3% |
Southwest Airlines flew 59.2% of the 11,911 flights listed. Frontier Airlines cancelled 1.48% of its flights here against 0.41% for SkyWest Airlines.
SkyWest Airlines arrived on time 15.1 percentage points more often than Frontier Airlines on this route.
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Sunday the least, a gap of 4.3 percentage points.
By month
- Jan: 81.2%
- Feb: 82.3%
- Mar: 78.4%
- Apr: 76.3%
- May: 69.2%
- Jun: 67.9%
- Jul: 67.5%
- Aug: 73.7%
- Sep: 83.4%
- Oct: 83.1%
- Nov: 86.2%
- Dec: 82.3%
July is historically the weakest month and November the strongest, a spread of 18.7 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 59.7% from 378 flights
- August 2023: 72.8% from 391 flights
- September 2023: 85.0% from 360 flights
- October 2023: 82.1% from 387 flights
- November 2023: 89.3% from 355 flights
- December 2023: 89.5% from 372 flights
- January 2024: 77.9% from 310 flights
- February 2024: 81.5% from 289 flights
- March 2024: 82.2% from 340 flights
- April 2024: 80.7% from 337 flights
- May 2024: 65.7% from 348 flights
- June 2024: 71.1% from 344 flights
- July 2024: 72.3% from 356 flights
- August 2024: 78.1% from 322 flights
- September 2024: 87.3% from 307 flights
- October 2024: 87.4% from 325 flights
- November 2024: 86.4% from 297 flights
- December 2024: 85.0% from 308 flights
- January 2025: 82.7% from 272 flights
- February 2025: 80.6% from 252 flights
- March 2025: 79.9% from 293 flights
- April 2025: 67.7% from 284 flights
- May 2025: 70.4% from 317 flights
- June 2025: 66.3% from 339 flights
- July 2025: 65.5% from 352 flights
- August 2025: 70.6% from 330 flights
- September 2025: 77.8% from 326 flights
- October 2025: 80.2% from 334 flights
- November 2025: 82.1% from 275 flights
- December 2025: 69.1% from 266 flights
- January 2026: 83.5% from 251 flights
- February 2026: 84.8% from 250 flights
- March 2026: 73.1% from 317 flights
- April 2026: 79.6% from 286 flights
- May 2026: 71.8% from 310 flights
- June 2026: 66.4% from 358 flights
- July 2026: 72.5% from 373 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 75.5% against 77.8% in the 12 months before — declining by 2.3 percentage points.
Data and methodology
Calculated by FlyerIntel from 11,911 STL → DEN flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed