St Louis Lambert International in May 2025

76.0%departed on time

BTS: A flight is counted as on time if it arrived less than 15 minutes after its scheduled time. Only carriers with at least 0.5 percent of domestic scheduled passenger revenue report.

In May 2025, reporting carriers scheduled 5,628 domestic departures from St Louis Lambert International (STL). 76.0% left less than 15 minutes late and 76.9% reached their destination on time; 1.2% were cancelled.

Nationally that month, 76.7% of flights departed on time and 75.4% arrived on time, so STL departures were 0.7 points below the national departure figure.

A year earlier, in May 2024, the airport had 5,656 departures with 70.2% leaving on time: a change of +5.8 points, with flights down 0%.

Flights arriving at STL that month were on time 77.9% of the time (5,634 scheduled arrivals).

Of the delay minutes that carriers assigned to a BTS cause category that month, late-arriving aircraft 38%, air carrier 29% and national aviation system 27%.

On time 76.9%
Arrived 15+ minutes late 21.7%
Cancelled 1.2%
Diverted 0.2%

Every scheduled departure from STL in May 2025, judged by arrival at the destination.

May 2025 against a year earlier, the airport's year and the nation

Measure	May 2025	May 2024	STL, 12 months to Jul 2026	All reported flights, May 2025
Departed on time	76.0%	70.2%	74.1%	76.7%
Arrived on time	76.9%	70.0%	76.8%	75.4%
Cancelled	1.2%	0.9%	1.3%	1.0%
Average departure delay (late minutes only)	15.7 min	22.2 min	17.6 min	17.5 min
Scheduled departures a day	188	189	174	20,188
Scheduled departures	5,628	5,656	63,318	605,648

Airlines that month

Reporting carrier	Flights	Share	On time	Avg arrival delay	Cancelled
WN Southwest Airlines	3,563	63%	75.9%	8.6 min	1.1%
AA American Airlines	575	10%	81.0%	10.7 min	1.0%
DL Delta Air Lines	483	9%	86.3%	-1.5 min	0.0%
UA United Airlines	269	5%	68.4%	19.2 min	0.7%
MQ Envoy Air	212	4%	69.3%	11.8 min	2.8%
YX Republic Airline	193	3%	73.6%	7.8 min	6.7%
OO SkyWest Airlines	131	2%	84.7%	3.2 min	0.0%
AS Alaska Airlines	79	1%	77.2%	4.4 min	1.3%
F9 Frontier Airlines	69	1%	73.9%	1.4 min	0.0%
OH PSA Airlines	40	1%	82.5%	-3.1 min	7.5%
NK Spirit Airlines	14	0%	78.6%	5.6 min	0.0%

Busiest routes that month

Route	Cities	Flights	On time	Avg arrival delay	Cancelled
STL–DEN	St. Louis to Denver	317	69.7%	17.8 min	0.6%
STL–ATL	St. Louis to Atlanta	302	79.5%	5.4 min	0.3%
STL–ORD	St. Louis to Chicago	284	78.2%	8.8 min	1.1%
STL–LGA	St. Louis to New York	221	70.6%	9.2 min	3.6%
STL–MCO	St. Louis to Orlando	218	73.4%	6.6 min	0.5%
STL–DFW	St. Louis to Dallas/Fort Worth	213	67.1%	21.4 min	2.8%
STL–PHX	St. Louis to Phoenix	209	77.0%	3.0 min	1.0%
STL–DCA	St. Louis to Washington	207	71.0%	15.0 min	1.9%
STL–CLT	St. Louis to Charlotte	180	83.3%	10.2 min	0.6%
STL–LAS	St. Louis to Las Vegas	173	76.9%	1.9 min	1.7%
STL–DAL	St. Louis to Dallas	172	76.2%	8.6 min	2.9%
STL–MDW	St. Louis to Chicago	166	81.3%	4.0 min	1.2%

By scheduled departure hour

On-time share:under 62%6270768288% and over

Share of departures that left less than 15 minutes late, by scheduled hour (local time), May 2025.

Delay causes

BTS cause category	Share of delay minutes	National, May 2025	Minutes
Air carrier	29.4%	29.3%	23,058
Late-arriving aircraft	38.3%	37.8%	29,962
National Aviation System	26.6%	25.9%	20,809
Extreme weather	5.4%	6.9%	4,256
Security	0.3%	0.1%	246

78,331 delay minutes on 1,220 flights that arrived 15 or more minutes late and carried a cause report. Carriers assign the categories; see what each category means.

Questions and answers

How many flights left STL on time in May 2025?

76.0% of 5,628 scheduled domestic departures left less than 15 minutes late, and 76.9% reached their destination on time. The national figures that month were 76.7% and 75.4%.

How does that compare with a year earlier?

In May 2024, 70.2% of 5,656 departures left on time and 0.9% were cancelled, against 76.0% and 1.2% in May 2025.

Provenance

Source: Bureau of Transportation Statistics, Reporting Carrier On-Time Performance, file for May 2025; public domain. Domestic scheduled flights by reporting carriers, totals and averages only. The site's data runs through July 2026. Full record for STL · methodology · corrections.