Delta, United, and JetBlue have round-trip flights from Denver (DEN) to New York (LGA) for $148-$163, NONSTOP. Flights August to October. 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.
Click for more details and booking links Nonstop Flights: Denver to/from New York $148-$163 r/t [August-October] – Delta / United / JetBlue