Route reliability record
MCI→STL
Kansas City to St. Louis
- Flights
- 1,020
- Period
- July 2025 to June 2026
- Distance
- 237 mi
- Carriers
- 1
This route earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.6%. When something does go wrong the average delay runs roughly 45 minutes. That rests on 1,020 MCI to STL flights, with a median arrival 9 minutes early.
Best time to fly MCI to STL: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 97.4% of the time and Wednesday flights 91.7%, against 86.2% for the route overall.
Set against the rest of the country, this route's record is 9 points better than the US average of 77.6%. That gap is worth roughly 86 fewer late arrivals for every thousand flights.
Key figures
On time
86.2%
Arrivals under 15 minutes late, of 1,015 completed flights
Avg delay
47 min
Across delayed arrivals only, not all flights
Cancelled
0.39%
National rate is 1.81%
Best carrier
Southwest
86.2% on time across 1,020 flights
These figures cover 1,020 flights between July 2025 and June 2026. The median arrival is 9 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 MCI to STL
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 | 86.2% | 47 min | 0.39% | A+ |
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 29 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–8am233 flights97.4%
- 8am–11am158 flights91.0%
- 11am–2pm245 flights86.8%
- 2pm–5pm184 flights86.4%
- 5pm–8pm200 flights68.5%
- 8pm–5am—
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 97.4% of the time, against 68.5% for the evening window. That is 29 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 245 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 17 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 77.8% on time, 17 points below February, the best at 94.4%. 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 92 flights.
Across the week, Wednesday is the strongest day at 91.7% on time and Thursday the weakest at 80.1%. 12 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 64% of the 6,537 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.
- 64%Late-arriving aircraft
- 22%Carrier
- 11%National Airspace System
- 2%Extreme weather
- 1%Security
64% 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 6,537 reported delay minutes here, that single category outweighs weather by 32 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 6,537 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 97.4% on time here.
Cancellations are rare at 0.39%, 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
Badly late arrivals are rare here: only 3.2% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
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 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 75.1% on time across 1,020 flights, 11 points below 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 STL 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 86.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,015 completed flights over 12 months sit behind that.
Common questions
MCI to STL questions
How often is MCI to STL delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 13.8% of the 1,020 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 45 minutes on average.
How reliable is MCI to STL compared with the rest of the country?
86.2% of flights arrive on time here against a national 77.6%, a difference of 9 points in its favour. That is worth a A+ on this site's grading scale.
What time of day has the fewest delays on MCI to STL?
The 5am–8am departure window is the strongest at 97.4% on time. The 5pm–8pm window is the weakest at 68.5%, 29 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 MCI to STL?
June is the weakest month at 77.8% on time, compared with 94.4% in February. Across the year that is 17 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 MCI — the return legseparate record
- Kansas City International (MCI) delay statistics
- St. Louis Lambert International (STL) delay statistics
- MCI to DEN, a related route76.1%
- ATL to STL, a related route82.4%
- MCI to ORD, a related route74.7%
- Southwest Airlines on-time record86.2%
- 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. MCI to STL and STL to MCI 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.