Route reliability record
HOU→STL
Houston to St. Louis
- Flights
- 1,544
- Period
- July 2025 to June 2026
- Distance
- 687 mi
- Carriers
- 1
This route lands a B+, 2 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 55 minutes on average. That is a workable record, not a spotless one. That rests on 1,544 HOU to STL flights, with a median arrival 5 minutes early.
Best time to fly HOU to STL: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 92.5% of the time and Tuesday flights 83.5%, against 79.7% 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
79.7%
Arrivals under 15 minutes late, of 1,535 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
0.26%
National rate is 1.81%
Best carrier
Southwest
79.7% on time across 1,544 flights
These figures cover 1,544 flights between July 2025 and June 2026. The median arrival is 5 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 HOU 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 | 1,544 | 79.7% | 53 min | 0.26% | 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 25 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–8am387 flights92.5%
- 8am–11am243 flights90.0%
- 11am–2pm178 flights74.0%
- 2pm–5pm230 flights75.5%
- 5pm–8pm270 flights70.3%
- 8pm–5am236 flights67.5%
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 92.5% of the time, against 67.5% for the overnight window. That is 25 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 387 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.
Delays peak in March, when the on-time rate falls to 67.8%. January is the strongest month at 93.3%. Moving a flexible trip across that boundary buys 26 points. July was the busiest month here, with 144 flights.
Across the week, Tuesday is the strongest day at 83.5% on time and Sunday the weakest at 72.5%. 11 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 52% of the 16,000 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.
- 52%Late-arriving aircraft
- 31%Carrier
- 13%National Airspace System
- 4%Extreme weather
- 1%Security
52% 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 16,000 reported delay minutes here, that single category outweighs weather by 13 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 16,411 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 92.5% on time here.
Cancellations are rare at 0.26%, 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
5.7% 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 roughly 55 minutes, which a normal layover absorbs.
The 687 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 79.3% on time across 1,533 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,544 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in STL after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 93.3% on time and March 67.8%, a swing of 26 points. If the dates move at all, move them out of March before you think about anything else. 1,535 completed flights over 12 months sit behind that.
Common questions
HOU to STL questions
How often is HOU to STL delayed?
About 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 20.3% of the 1,544 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 55 minutes on average.
How reliable is HOU to STL compared with the rest of the country?
79.7% of flights arrive on time here against a national 77.6%, a difference of 2 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on HOU to STL?
The 5am–8am departure window is the strongest at 92.5% on time. The 8pm–5am window is the weakest at 67.5%, 25 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 March delays on HOU to STL?
March is the weakest month at 67.8% on time, compared with 93.3% in January. 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
- STL to HOU — the return legseparate record
- William P. Hobby (HOU) delay statistics
- St. Louis Lambert International (STL) delay statistics
- HOU to DAL, a related route80.9%
- ATL to STL, a related route82.4%
- HOU to ATL, a related route79.8%
- Southwest Airlines on-time record79.7%
- 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. HOU to STL and STL to HOU 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.