I haven’t seen this discussed elsewhere. The route of one flight I’m following includes the term D+00 twice. Looking at its green line, I see that after reaching the waypoint preceding the D+00 entry the airplane has gone into a series of circles (or maybe a holding pattern). So does the D+00 denote some sort of delay?
Sorry, that should have read D1+00, NOT D+00.
It means delay of 1 hour. D(H)+(MM), so D1+00 = 1hr/60min.
Usually requested when filing IFR by the pilots for whatever reason necessary (e.g., training, photography, etc).