If you want a cheap flight from Las Vegas to Washington DC, you've got one airlines to choose from.
You can use the filters on your search to see more flights and find cheaper rates – Washington DC has more than one airport. So if you don't need to fly into Washington DC Washington Dulles International Airport, it's worth checking your other options. The 3319 km flight usually takes about 6 hrs 45 mins.
During this peak season, hotel and holiday prices often increase too, so it's best to book early. Or you could keep your fingers crossed and hold out for a last-minute deal.