Route
SEA → STL
Seattle–Tacoma International Airport St. Louis Lambert International Airport
1,709 miles
Return route STL → SEA →
How punctual is this route?
- On-time arrivals
- 84.4%
- Less than 15 minutes late
- Cancelled
- 0.3%
- Of scheduled flights
- Average delay when late
- 55 min
- Flights arriving 15+ minutes late
- Flights tracked
- 883
- Scheduled flights in the period
What caused the delays
- Airline (crew, maintenance, cleaning) 42%
- Late-arriving aircraft 35%
- Air traffic control & airport 18%
- Extreme weather 4%
- Security 1%
Share of delay minutes airlines attributed to each cause (BTS).
Sep 2025
Aug 2026
Show as table
| Month | On time | Flights |
|---|---|---|
| September 2025 | 73.5% | 98 |
| October 2025 | 85.2% | 61 |
| November 2025 | 84.0% | 50 |
| December 2025 | 79.6% | 54 |
| January 2026 | 91.7% | 37 |
| February 2026 | 97.4% | 38 |
| March 2026 | 94.1% | 52 |
| April 2026 | 100.0% | 60 |
| May 2026 | 81.5% | 81 |
| June 2026 | 88.9% | 118 |
| July 2026 | 84.4% | 123 |
| August 2026 | 73.9% | 111 |
Source: U.S. DOT Bureau of Transportation Statistics on-time data, September 2025 – August 2026. Covers flights operated by reporting U.S. carriers. About our data
Airlines on this route
| Airline | Flights | On time | Cancelled | Avg. delay when late |
|---|---|---|---|---|
| Alaska Airlines | 780 | 85.8% | 0.3% | 53 min |
| Southwest Airlines | 103 | 73.5% | 1.0% | 62 min |
Delay odds by flight
How often each flight number arrived 15 or more minutes late over the last year.
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