Singapore to Washington, D.C. $674 Return on Air China
Air China is having a sale on lots of destinations. Of note is Washington D.C. which is at $674 return if you plug the dates into Skyscanner. You can all the cheap dates in Flightscout. Alternatively you can just book directly with Air China for a little bit more. Dates are March.
All fares include seat selection, meals and bags. This is the cheapest flight to Washington D.C on CCL ever and beats the next best flight by $178.