American Airlines, United, and JetBlue have round-trip flights from Dallas (DFW) to Boston or San Francisco (BOS, SFO) for $157-$168, NONSTOP. Flights January to March. Most dates are on Tuesdays, Wednesdays, and Saturdays. Extended weekends available. Origin/Destination reversible.
A Carry-on bag and also a personal item is allowed for free on American. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.