Seattle-Tacoma International Airport (SEA)
Seattle-Tacoma International Airport (SEA) carries at least 5% of the passengers on 8 of the 100 busiest US routes. On those routes about 17.5 million passengers flew through it in 2025, counting each route's airport split.
CO2 on the routes through SEA
The routes through SEA run from 119 kg of CO2 per passenger (San Francisco to Seattle) to 220 kg (Chicago to Seattle), with a middle of 164 kg.
Every route that uses SEA, busiest first
| Route | Flown with | Share through SEA | kg CO2 per passenger |
|---|---|---|---|
| Los Angeles to Seattle | LAX (49%), SNA (24%), ONT (16%) | 100% | 151 |
| San Francisco to Seattle | SFO (52%), SJC (30%), OAK (18%) | 100% | 119 |
| Seattle to Phoenix | PHX (100%) | 100% | 164 |
| Denver to Seattle | DEN (100%) | 100% | 135 |
| Seattle to Anchorage | ANC (100%) | 100% | 203 |
| Chicago to Seattle | ORD (91%), MDW (10%) | 100% | 220 |
| Dallas-Fort Worth to Seattle | DFW (96%), DAL (4%) | 100% | 211 |
| Las Vegas to Seattle | LAS (100%) | 100% | 128 |
Airport references
Source: US Bureau of Transportation Statistics (BTS), T-100 traffic and Schedule T-2 fuel filings; US EPA jet-fuel CO2 factor. Route calculation method.
Airlines on these routes
By passengers on the routes above, the largest are Alaska Airlines, Delta Air Lines, Southwest Airlines, United Airlines, American Airlines and SkyWest Airlines.
About these figures. The CO2 per passenger is for the whole city pair, so it covers every airport the route uses. The airline filings the figures come from don't split fuel by airport, so we can't say how a flight from SEA compares with one from a neighbouring airport. The share column is the part of the route's passengers that flew through SEA, from the same filings. How the figures are built.