The Russian diplomats have to leave the US before Monday, so they have until Monday to depart.
The US State Dept allowed Russia to send a large plane, a Iluysin II plane to land at Dulles Airport outside of DC.
The arrival has been documented. ( this is a stock photo, not at Dulles)
As Dulles is a busy airport, there are regular commercial flights scheduled as far out as I can see ( till Tuesday, March 8), but RSD88 is not yet listed.
They will have to list the departure in the next day or so for Dulles to keep up the regular schedule. I'll check back.