Airport month record
STLAPR
St. Louis Lambert International in April 2026
- Departures
- 5,156
- Month
- April 2026
- National, same month
- 79.8%
- Carriers
- 10
Historical statistics for April 2026, not live status or a forecast for this year’s April. For today’s conditions at STL, see live FAA status.
STL in April lands a B+, about a point better than the national rate of 79.8%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 5,156 flights, of which Delta Air Lines flew 422 at 89.0% on time.
Delta Air Lines is the most reliable of the three carriers covered here at 89.0% on time across 422 flights.
Key figures
On time
80.8%
Arrivals under 15 minutes late, of 5,107 completed departures
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
0.80%
Nationally in April: 0.90%
Whole year
78.0%
STL across all twelve months
These figures cover 5,156 departures from St. Louis Lambert International in April 2026. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.
Against the year
April next to STL's other months
Against STL's own year, April ran 3 points better than the twelve-month rate of 78.0%, which makes it number four of twelve months, best first. Either side of it, March ran 75.3% on time and May 77.5%, so a trip moved by a few weeks would have landed in a worse stretch.
| Month | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| July 2025 | 5,855 | 71.7% | 73 min | 1.57% | C |
| August 2025 | 5,539 | 79.7% | 71 min | 0.96% | B+ |
| September 2025 | 5,321 | 83.8% | 58 min | 0.34% | B+ |
| October 2025 | 5,611 | 78.5% | 60 min | 0.27% | B+ |
| November 2025 | 5,202 | 80.1% | 76 min | 1.46% | B |
| December 2025 | 5,359 | 74.0% | 75 min | 0.90% | C+ |
| January 2026 | 4,683 | 83.1% | 74 min | 3.46% | B− |
| February 2026 | 4,484 | 84.9% | 64 min | 1.32% | B |
| March 2026 | 5,400 | 75.3% | 74 min | 2.52% | B |
| April 2026 (this page) | 5,156 | 80.8% | 65 min | 0.80% | B+ |
| May 2026 | 5,375 | 77.5% | 74 min | 0.84% | B+ |
| June 2026 | 5,463 | 69.0% | 68 min | 1.17% | C |
Departure window
The best time of day to leave STL in April
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am970 flights91.3%
- 8am–11am1,192 flights87.2%
- 11am–2pm698 flights83.8%
- 2pm–5pm831 flights76.0%
- 5pm–8pm895 flights71.7%
- 8pm–5am570 flights67.1%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.3% of the time, against 67.1% for the overnight window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 1,192 flights scheduled in it.
Across the week, Saturday is the strongest day at 86.4% on time and Monday the weakest at 73.9%. 13 points is a smaller lever than departure hour, but it is free.
Carrier by carrier
Which airlines ran best at STL in April
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 89.0% of the time; Southwest Airlines manages 79.7%. Sample sizes sit next to every figure, because a two-point gap across 3,162 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 3,162 | 79.7% | 49 min | 0.19% | B+ |
| American Airlines | 524 | 83.7% | 111 min | 1.34% | B |
| Delta Air Lines | 422 | 89.0% | 75 min | 1.18% | A |
| Republic Airwaysthin sample | 287 | 83.0% | 58 min | 1.05% | B |
| SkyWest Airlinesthin sample | 228 | 68.8% | 101 min | 3.95% | C− |
| Envoy Airthin sample | 149 | 76.0% | 152 min | 2.01% | B |
| United Airlinesthin sample | 142 | 84.9% | 47 min | 2.11% | B |
| Frontier Airlinesthin sample | 97 | 75.8% | 87 min | 2.06% | B |
| PSA Airlinesthin sample | 85 | 83.1% | 83 min | 1.18% | B |
| Alaska Airlinesthin sample | 60 | 94.8% | 193 min | 3.33% | A− |
Delta leads Southwest by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Route by route
Busiest routes out of STL in April
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| STL to ATL · Atlantathin sample | 299 | 86.0% | 87 min | 2.01% | A |
| STL to ORD · Chicagothin sample | 294 | 71.8% | 131 min | 5.10% | C− |
| STL to DEN · Denverthin sample | 286 | 79.6% | 47 min | 0.70% | B+ |
| STL to LGA · New Yorkthin sample | 249 | 77.2% | 53 min | 0.40% | B+ |
| STL to MCO · Orlandothin sample | 228 | 85.9% | 48 min | 0.44% | A+ |
| STL to PHX · Phoenixthin sample | 207 | 79.7% | 82 min | 0.00% | B+ |
| STL to DCA · Washingtonthin sample | 193 | 81.8% | 56 min | 0.00% | B+ |
| STL to MSP · Minneapolisthin sample | 183 | 82.5% | 57 min | 0.00% | B+ |
| STL to DFW · Dallas-Fort Worththin sample | 180 | 77.7% | 80 min | 2.22% | B |
| STL to DTW · Detroitthin sample | 167 | 86.2% | 62 min | 0.00% | A+ |
| STL to LAS · Las Vegasthin sample | 167 | 70.5% | 55 min | 0.60% | C+ |
| STL to DAL · Dallasthin sample | 158 | 79.5% | 42 min | 1.27% | B |
| STL to MDW · Chicagothin sample | 150 | 83.8% | 70 min | 0.67% | B+ |
| STL to BOS · Bostonthin sample | 134 | 67.9% | 58 min | 0.00% | C+ |
| STL to HOU · Houstonthin sample | 131 | 86.3% | 49 min | 0.00% | A+ |
| STL to PHL · Philadelphiathin sample | 129 | 85.9% | 57 min | 0.78% | A+ |
| STL to CLT · Charlottethin sample | 123 | 91.9% | 89 min | 0.00% | A+ |
| STL to BNA · Nashvillethin sample | 111 | 86.5% | 45 min | 0.00% | A+ |
| STL to TPA · Tampathin sample | 110 | 83.6% | 51 min | 0.00% | B+ |
| STL to BWI · Baltimorethin sample | 107 | 86.9% | 72 min | 0.00% | A+ |
| STL to MIA · Miamithin sample | 96 | 93.8% | 60 min | 0.00% | A+ |
| STL to RSW · Fort Myersthin sample | 91 | 87.8% | 66 min | 0.00% | A+ |
| STL to AUS · Austinthin sample | 89 | 79.8% | 49 min | 0.00% | B+ |
| STL to MCI · Kansas Citythin sample | 86 | 73.3% | 62 min | 0.00% | C+ |
| STL to EWR · Newarkthin sample | 86 | 91.8% | 77 min | 1.16% | A |
Delay causes
What held STL up in April
One category carries most of the weight here. Late-arriving aircraft accounts for 45% of the 64,000 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.
- 45%Late-arriving aircraft
- 28%Carrier
- 21%National Airspace System
- 6%Extreme weather
- 0%Security
45% 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 64,000 reported delay minutes here, that single category outweighs weather by 8 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 63,957 reported delay minutes.
Cancellations are rare at 0.80%, below the national 0.90% 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.
5.9% of arrivals land an hour or more late, close to the national 6.4%. 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 an hour, which a normal layover absorbs.
What to do with this
Flying from STL in April
For a April trip through STL: expect 80.8% on time and 0.80% cancelled, going by April 2026. The 5am–8am window was the strongest part of the day.
Related
Where to go next
- St. Louis Lambert International (STL), the whole year
- STL in July71.7%
- STL in August79.7%
- STL in September83.8%
- STL in October78.5%
- STL in November80.1%
- STL in December74.0%
- STL in January83.1%
- STL in February84.9%
- STL in March75.3%
- STL in May77.5%
- STL in June69.0%
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.