Ending today, Frontier Airlines offers 1-way fares with prices starting at $35. (Click on "Frontier Airlines" in the headline to see this sale; all taxes are included.) That's tied with our mention from two weeks ago as the lowest base fare we've seen from Frontier this year. It's also a current low for select routes by $355. This price is valid on flights departing from Denver, CO, (DEN) with arrival in Sioux City, IA, (SUX) on June 15; prices vary depending on the departure cities and dates chosen. Book this travel deal today for travel through November 19. Other notable fares: