Most travellers find the cheapest return flights to Washington when choosing a flight departing in February.
On average, from most locations, when planning your trip to Washington, try to book your flight in the region of 60 days in advance for the cheapest prices.
From most locations, the cheapest flights to Washington are found on a Wednesday. Booking a Sunday departure is usually the most expensive.
On average you can find the best deals on plane tickets to Washington when looking for flights with midday departure times.