Route reliability record
MSY→STL
New Orleans to St. Louis
- Flights
- 731
- Period
- July 2025 to June 2026
- Distance
- 604 mi
- Carriers
- 1
This route lands a B+, 4 points better than the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about 50 minutes on average. That is a workable record, not a spotless one. That rests on 731 MSY to STL flights, with a median arrival 8 minutes early.
Best time to fly MSY to STL: a 8am–11am departure, ideally on a Tuesday. Flights in that window arrived on time 97.8% of the time and Tuesday flights 89.2%, against 81.8% for the route overall.
Set against the rest of the country, this route's record is 4 points better than the US average of 77.6%. That gap is worth roughly 42 fewer late arrivals for every thousand flights.
Key figures
On time
81.8%
Arrivals under 15 minutes late, of 726 completed flights
Avg delay
51 min
Across delayed arrivals only, not all flights
Cancelled
0.41%
National rate is 1.81%
Best carrier
Southwest
81.8% on time across 731 flights
These figures cover 731 flights between July 2025 and June 2026. The median arrival is 8 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 MSY 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 | 731 | 81.8% | 51 min | 0.41% | 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 32 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–8am299 flights93.9%
- 8am–11am45 flights97.8%
- 11am–2pm50 flights84.0%
- 2pm–5pm45 flights71.1%
- 5pm–8pm254 flights68.5%
- 8pm–5am38 flights65.8%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 97.8% of the time, against 65.8% for the overnight window. That is 32 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 299 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 24 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.
Delays peak in May, when the on-time rate falls to 71.7%. January is the strongest month at 95.2%. Moving a flexible trip across that boundary buys 24 points. October was the busiest month here, with 82 flights.
Across the week, Tuesday is the strongest day at 89.2% on time and Sunday the weakest at 70.2%. 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 70% of the 6,681 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.
- 70%Late-arriving aircraft
- 21%Carrier
- 5%National Airspace System
- 2%Extreme weather
- 1%Security
70% 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 6,681 reported delay minutes here, that single category outweighs weather by 33 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 6,681 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 97.8% on time here.
Cancellations are rare at 0.41%, 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
5.8% 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 50 minutes, which a normal layover absorbs.
The 604 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 83.7% on time across 732 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 731 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. 731 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 81.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 726 completed flights over 12 months sit behind that.
Common questions
MSY to STL questions
How often is MSY to STL delayed?
Roughly one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.2% of the 731 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 50 minutes on average.
How reliable is MSY to STL compared with the rest of the country?
81.8% of flights arrive on time here against a national 77.6%, a difference of 4 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on MSY to STL?
The 8am–11am departure window is the strongest at 97.8% on time. The 8pm–5am window is the weakest at 65.8%, 32 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 May delays on MSY to STL?
May is the weakest month at 71.7% on time, compared with 95.2% in January. Across the year that is 24 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 MSY — the return legseparate record
- Louis Armstrong New Orleans International (MSY) delay statistics
- St. Louis Lambert International (STL) delay statistics
- MSY to ATL, a related route83.3%
- ATL to STL, a related route82.4%
- MSY to IAH, a related route82.2%
- Southwest Airlines on-time record81.8%
- 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. MSY to STL and STL to MSY 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.