How reliable is St Louis Lambert International Airport?
Flights from STL departed within 15 minutes of schedule in 79% of 385,463 flights in official BTS history — and weather is calmest in Sep. Here’s the full picture before you book.
Reliability score
on-time, cancellations & delays
Weather favorability
year-round climate
Origin-airport operations
What the departure punctuality at STL looks like
On-time departures
across 385,463 flights
Source: BTS Airport Operations · data through 2026-06-25. Role-specific BTS departure history; advisory context, not a guarantee for any flight.
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Weather by month
When the weather works for you at St. Louis
A calm-weather score (0–100) for each month from decades of airport observations — how often conditions disrupt flying, not temperature. Higher is calmer.
Calmest month
Calmest flying weather of the year · 96/100 favorability
Roughest month
Most disruptive — low visibility & fog, snow · 79/100 favorability
The read on STL
What the numbers say about flying through St Louis Lambert International Airport
Across official performance history, flights from St. Louis left within 15 minutes of schedule about 79% of the time over 385,463 flights. That's a respectable but unspectacular operational record. Pair it with a moderate cancellation rate of 1.6%. When a departure does run late, the typical delay is around 12 minutes.
On weather, St. Louis is an unusually calm-weather airport year-round. September is the calmest stretch for flying, scoring 96 out of 100 for favorable conditions, while January is the most disruptive at 79, driven mainly by low visibility & fog and snow. The year is relatively steady, so no single month stands out as one to avoid on weather alone.
None of this guarantees your specific flight — it’s the backdrop. To turn it into a booking, score real flights to St. Louis, read how we weigh it all in how the PlaneSane Score works, and brush up with how to pick a reliable flight and avoiding weather delays.
Common questions about STL
- How reliable is St Louis Lambert International Airport (STL)?
- Flights from St. Louis left within 15 minutes of schedule roughly 79% of the time across 385,463 flights of official history — a respectable but unspectacular operational record. The cancellation rate runs about 1.6%. It's advisory context, not a guarantee for any single flight.
- What is the best month to fly from STL for good weather?
- September has the calmest flying weather at St Louis Lambert International Airport. January is the most disruptive, mainly from low visibility & fog and snow.
Planning a trip through St. Louis?
Score real flights to and from STL on reliability, weather, and connection safety — not just price.