Germany's Condor airline will become Sea-Tac's fifth European carrier in June as it inaugurates service to Frankfurt.
Condor, a division of tour giant Thomas Cook, will fly the route on Mondays and Thursdays with Boeing 767 aircraft.
Germany’s largest airline, Lufthansa, also offers service on the route. Lufthansa connects Sea-Tac with Frankfurt daily.
Sea-Tac has three other European carriers: Air France with service to Paris, British with non-stops to London and Icelandic with service to Reykjavik. American carrier Delta also flies nonstop from Sea-Tac to Amsterdam.