This fare looks to be mirroring the Alaska Sale fares we mentioned earlier today. When searching on Delta we found seats departing SEA on Saturday, May 26 and returning from BOS on Wednesday, May 30, 2018. This fare looks to be available for departures through mid-June. Flights are also available in March and April by JetBlue and Alaska, but it looks like Delta has stretched the calendar into June. Travel days will vary by airline but many dates seem to be available at the moment.
Have a look at all of our flights departing Seattle SEA on the fare details page here.
Need a room in Boston over the long weekend? These deals are available for the listed dates on Hotelwatchdog.