Buying a cheap ticket to Las Vegas depends totally upon your itinerary and the destination you are flying from. But if you are looking for an answer to what is the cheapest month to fly to Las Vegas, then January can be your best bet. If you book your ticket in January, you are most likely to get a 10% discount on your average ticket booking. Or, you can make the purchase one month before the scheduled departure if you want to get the last-minute deal on your tickets.