Route on-time record
STL to DEN: most on-time flights and the best time to fly
St Louis (St. Louis Lambert International Airport) to Denver (Denver International Airport). 3,636 nonstop flights in Jun 2025 to May 2026, 75% arrived within 15 minutes and 0.3% were cancelled. The most reliable flight number was Southwest 4454 at 6:20 AM.
Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.
STL → DEN
St Louis to Denver: 3,636 nonstop flights a year
On time (12 months)
75%
Cancelled
0.3%
avg delay 19 min
Best time to leave
Before 9 AM
90% on time vs 54% 3 to 6 PM
Most reliable airline
SkyWest
85% chance on time
Lowest nonstop fare seen in the next two months: $236 (Frontier 4567 on 2026-10-24). Fares open on our travel partner (Aviasales). Pick the flight number you chose here.
Most reliable nonstop flights
Ranked by the chance the flight operates and arrives within 15 minutes of schedule, from Jun 2025 to May 2026 records.
#1 · Southwest 4454
6:20 AM → 7:40 AM2h 20m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Southwest 3852; its record covers all of them.
94%
chance on time
- On time (history)
- 98%
- Cancelled
- 0.0%
- Avg arrival delay
- 1 min
- Arrived on time 98% of the time (87 flights, Jun 2025 to May 2026).
- Never cancelled in 87 scheduled flights.
- Leaves in this route's most on-time window (Before 9 AM: 90% on time; 3 to 6 PM: 54%).
Moderate track record · 87 flights
Find Southwest 4454 fares Opens this date on Aviasales#2 · SkyWest 5620 · sold as United Express, Delta Connection, American Eagle or Alaska
5:15 AM → 6:55 AM2h 40m nonstop
Local times, typical schedule. Last flown 2026-03-28.
89%
chance on time
- On time (history)
- 82%
- Cancelled
- 4.3%
- Avg arrival delay
- 19 min
- Arrived on time 82% of the time (22 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 90% on time; 3 to 6 PM: 54%).
- Short track record (22 flights), so its score leans on the airline's record at this hour.
Limited track record · 22 flights
Find 5:15 AM flight fares Opens this date on Aviasales#3 · United 362
5:10 AM → 6:32 AM2h 22m nonstop
Local times, typical schedule. Last flown 2026-05-31.
88%
chance on time
- On time (history)
- 91%
- Cancelled
- 0.0%
- Avg arrival delay
- 2 min
- Arrived on time 91% of the time (11 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 90% on time; 3 to 6 PM: 54%).
- Short track record (11 flights), so its score leans on the airline's record at this hour.
Limited track record · 11 flights
Find United 362 fares Opens this date on Aviasales#4 · United 1380
2:40 PM → 4:14 PM2h 34m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as United 1729; its record covers all of them.
84%
chance on time
- On time (history)
- 87%
- Cancelled
- 0.0%
- Avg arrival delay
- 9 min
- Arrived on time 87% of the time (91 flights, Jun 2025 to May 2026).
- Never cancelled in 91 scheduled flights.
- Lands inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
Moderate track record · 91 flights
Find United 1380 fares Opens this date on Aviasales#5 · United 1415
8:54 AM → 10:27 AM2h 33m nonstop
Local times, typical schedule. Last flown 2026-04-29.
84%
chance on time
- On time (history)
- 90%
- Cancelled
- 3.1%
- Avg arrival delay
- 5 min
- Arrived on time 90% of the time (31 flights, Jun 2025 to May 2026).
- Cancelled 3.1% of the time (1 of 32).
- Leaves in this route's most on-time window (Before 9 AM: 90% on time; 3 to 6 PM: 54%).
- Short track record (31 flights), so its score leans on the airline's record at this hour.
Limited track record · 31 flights
Find United 1415 fares Opens this date on Aviasales#6 · United 2459
9:06 AM → 10:30 AM2h 24m nonstop
Local times, typical schedule. Last flown 2026-05-31.
83%
chance on time
- On time (history)
- 100%
- Cancelled
- 0.0%
- Avg arrival delay
- 0 min
- Arrived on time 100% of the time (10 flights, Jun 2025 to May 2026).
- Short track record (10 flights), so its score leans on the airline's record at this hour.
Limited track record · 10 flights
Find United 2459 fares Opens this date on Aviasales#7 · United 1396
9:00 AM → 10:36 AM2h 36m nonstop
Local times, typical schedule. Last flown 2026-03-28.
82%
chance on time
- On time (history)
- 82%
- Cancelled
- 0.4%
- Avg arrival delay
- 15 min
- Arrived on time 82% of the time (269 flights, Jun 2025 to May 2026).
Strong track record · 269 flights
Find United 1396 fares Opens this date on Aviasales#8 · United 333
2:50 PM → 4:26 PM2h 36m nonstop
Local times, typical schedule. Last flown 2026-03-28.
81%
chance on time
- On time (history)
- 83%
- Cancelled
- 0.0%
- Avg arrival delay
- 18 min
- Arrived on time 83% of the time (24 flights, Jun 2025 to May 2026).
- Lands inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
- Short track record (24 flights), so its score leans on the airline's record at this hour.
Limited track record · 24 flights
Find United 333 fares Opens this date on Aviasales#9 · United 1302
8:46 AM → 10:20 AM2h 34m nonstop
Local times, typical schedule. Last flown 2026-05-20.
81%
chance on time
- On time (history)
- 80%
- Cancelled
- 4.8%
- Avg arrival delay
- 37 min
- Arrived on time 80% of the time (20 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 90% on time; 3 to 6 PM: 54%).
- 83% of its delay minutes came from the plane arriving late from an earlier flight.
- Short track record (20 flights), so its score leans on the airline's record at this hour.
Limited track record · 20 flights
Find United 1302 fares Opens this date on Aviasales#10 · Southwest 3562
11:30 AM → 12:50 PM2h 20m nonstop
Local times, typical schedule. Last flown 2026-05-31.
81%
chance on time
- On time (history)
- 82%
- Cancelled
- 0.0%
- Avg arrival delay
- 9 min
- Arrived on time 82% of the time (55 flights, Jun 2025 to May 2026).
- Never cancelled in 55 scheduled flights.
- Short track record (55 flights), so its score leans on the airline's record at this hour.
Limited track record · 55 flights
Find Southwest 3562 fares Opens this date on Aviasales
Airlines on this route
Season-adjusted chance of operating and arriving on time.
- SkyWest Airlines (sold as United Express, Delta Connection, American Eagle or Alaska)85%
172 flights · 88% on time as flown · 0.5% cancel
- Frontier Airlines75%
264 flights · 76% on time as flown · 0.6% cancel
- United Airlines74%
1,041 flights · 75% on time as flown · 0.4% cancel
- Southwest Airlines74%
2,159 flights · 74% on time as flown · 0.2% cancel
On time by departure time
All airlines, scheduled local departure, Jun 2025 to May 2026.
- Before 9 AM90%
1,013 flights · avg delay 7 min
- 9 AM to noon82%
476 flights · avg delay 11 min
- Noon to 3 PM81%
709 flights · avg delay 14 min
- 3 to 6 PM54%
706 flights · avg delay 40 min
- 6 to 9 PM65%
600 flights · avg delay 28 min
- After 9 PM60%
132 flights · avg delay 23 min
On time by month
All airlines, Jun 2023 to May 2026. Several years per month, so one stormy season doesn't define a month. Travel-month estimates use this seasonal pattern.
What delays this route
- Late-arriving aircraft38%
- Air traffic control and airport volume36%
- Airline (crew, maintenance, boarding)23%
- Severe weather4%
Share of delay minutes by the cause airlines report to the US DOT.
Historical odds, not a guarantee. Built from the US DOT Bureau of Transportation Statistics on-time reports (Jun 2025 to May 2026), FAA ground stop and delay program advisories, and 20 years of airport weather observations. Covers US airlines that report to the DOT; schedules are flights operated recently, so confirm times when you book. ATIS Alerts is not affiliated with any airline. Fares are what Aviasales travelers saw in recent searches (USD, one way, 1 adult), not live quotes; the partner site shows the current price. Fare links go to our travel partner and may earn us a commission at no cost to you. Affiliate disclosure
STL to DEN questions
- What time of day is best to fly STL to DEN?
- Before 9 AM: 90% of flights arrived on time, against 54% for departures 3 to 6 PM. Later flights inherit delays from earlier ones, so the first departures of the day usually run best.
- Which airline is most on time from STL to DEN?
- SkyWest, with a season-adjusted 85% chance of operating and arriving on time over 172 flights. The adjustment compares each airline with what the route did in the months it flew, so a carrier that skipped a stormy month gets no free credit.
- What is the worst month for delays on STL to DEN?
- July (66% on time); the best was November (86%), averaged over Jun 2023 to May 2026.
- Is this a prediction for my flight?
- No. These are historical odds from the US DOT on-time reports, FAA advisories and airport weather records. Check your flight status and the FAA delay board on the day you fly.
More routes from STL
- DEN to STL (return)
- STL to ATL 85%
- STL to ORD 71%
- STL to LGA 75%
- STL to MCO 78%
- STL to DCA 73%
- STL to DFW 74%
- STL to PHX 76%
- STL to LAS 79%
- STL to DAL 77%
- STL to DTW 83%
- STL to MSP 80%
- STL to CLT 83%
Live status: FAA delays and ground stops