If you want a cheap flight from Manchester to Washington DC, you've got four airlines to choose from.
Make sure you use the search options above to search for flights to other airports in Washington DC, not just Washington DC Ronald Reagan Washington National Airport. The more options you look at, the better your chance of finding a cheap deal. Just so you know, the flight typically takes 11 hrs 25 mins.
Flights from Manchester to are usually most expensive during May. If you're planning on going to Washington DC during this time, you could take a look at other airport options. Or you could try to get a last-minute bargain.