SEATAC, Wash. — Thursday marks the busiest travel day for the July 4th holiday at Seattle-Tacoma International Airport. If you’re heading to the airport, you’re going to want to get there early to get through on time. It’s busy season in Seattle: this week includes World Cup fans, cruise passengers, the July 4th holiday, and general tourist traffic. All this adds up to 204,000 people expected to move through SEA today, according to airport officials.