We are seeing several US cities with flights to Singapore (SIN) for $649 round-trip, on a deep-discounted unadvertised sale today. These flights are operated by United Airlines undercutting Delta hub cities. Sales like these don't last very long so book fast if interested.
Seats are available for travel from February through early June then again from August through December. Dates vary per route, but those travel windows seem to be where most availability can be found. Unfortunately, peak Summer and Holiday dates are blacked-out. Travel is available Monday through Thursday.
As an example below, we found flights departing ATL on Thursday, May 3 and returning from SIN on Thursday, May 10, 2018. Click on the fare details below for more information:
Need a hotel in Singapore? Here is what is available for the mentioned dates on Hotelwatchdog.