Hawaiian, American Airlines, Delta, Southwest and various other airlines have round-trip flights from Dallas (DFW/DAL) to Seattle (SEA) for $174-$191, NONSTOP or with connections. Flights March to May. Departures on Monday, Tuesday, Wednesday, Thursday, and Saturday. Extended weekends available. Origin/Destination reversible.
A Carry-on bag and also a personal item is allowed for free on Delta. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.