Frontier Airlines is returning to Billings Logan International Airport  with a nonstop flight, three days a week to Denver.  The news was announced yesterday with a mention of starting at $39.  I don't know if this is a start up gimmick or if the price will stay.  Frontier route planner Jonathon Nield says the airline is expected to begin service in Billings on May 30.

Flights will be on Tuesdays, Thursdays and Sundays and may be booked now from Frontier's website.

Flights departing Denver for Billings will take off at 9:55 a.m. and arrive at 11:28 a.m. Flights from Billings to Denver will depart at 12:20 p.m. and arrive at 1:53 p.m.

Passengers will fly on an Airbus A320 aircraft with seating capacity of between 180 and 186.

Frontier has served Billings in the past. It most recently dropped service to Billings in 2013.

I would assume that if you can get to Denver for $40 you can find cheaper flights from there. Many people in the Billings area are willing drive to Bozeman to get cheaper rates.