Route reliability record
STL→MCI
St. Louis to Kansas City
- Flights
- 1,020
- Period
- July 2025 to June 2026
- Distance
- 237 mi
- Carriers
- 1
This route sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.6%. The late ones land about 55 minutes behind schedule. That rests on 1,020 STL to MCI flights, with a median arrival 3 minutes early.
Best time to fly STL to MCI: a 11am–2pm departure, ideally on a Wednesday. Flights in that window arrived on time 94.4% of the time and Wednesday flights 82.1%, against 75.1% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
75.1%
Arrivals under 15 minutes late, of 1,017 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.29%
National rate is 1.81%
Best carrier
Southwest
75.1% on time across 1,020 flights
These figures cover 1,020 flights between July 2025 and June 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.
Carrier by carrier
Which airline is most reliable on STL to MCI
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 1,020 | 75.1% | 55 min | 0.29% | B+ |
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 37 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am358 flights90.2%
- 11am–2pm54 flights94.4%
- 2pm–5pm247 flights70.4%
- 5pm–8pm62 flights75.8%
- 8pm–5am299 flights57.1%
Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 57.1% on time, against 94.4% for the 11am–2pm 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 358 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 26 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.
December is the weak month at 59.5% on time, against 85.2% in November. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 92 flights.
Across the week, Wednesday is the strongest day at 82.1% on time and Sunday the weakest at 62.9%. 19 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 59% of the 14,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 59%Late-arriving aircraft
- 25%Carrier
- 10%National Airspace System
- 6%Extreme weather
59% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 14,000 reported delay minutes here, that single category outweighs weather by 10 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 13,856 reported delay minutes.
Cancellations are rare at 0.29%, below the national 1.81% 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.
Connections and stage length
What a delay here actually costs
7.1% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says 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.
At 237 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 11am–2pm window matters as much as it does.
The return leg is a different operation and performs like one: it runs 86.2% on time across 1,020 flights, 11 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 11 points of difference.
One caution: this is a thin sample. 1,020 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
Work out the risk of missing a connection in MCI after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 1,020 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 75.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,017 completed flights over 12 months sit behind that.
Common questions
STL to MCI questions
How often is STL to MCI 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 24.9% of the 1,020 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 55 minutes on average.
How reliable is STL to MCI compared with the rest of the country?
75.1% of flights arrive on time here against a national 77.6%, a difference of 3 points against it. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on STL to MCI?
The 11am–2pm departure window is the strongest at 94.4% on time. The 8pm–5am window is the weakest at 57.1%, 37 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 December delays on STL to MCI?
December is the weakest month at 59.5% on time, compared with 85.2% in November. Across the year that is 26 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
- MCI to STL — the return legseparate record
- St. Louis Lambert International (STL) delay statistics
- Kansas City International (MCI) delay statistics
- STL to ATL, a related route85.3%
- DEN to MCI, a related route75.5%
- STL to DEN, a related route74.9%
- Southwest Airlines on-time record75.1%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. STL to MCI and MCI to STL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.