Just appeared on 'My Flights' at FL490, N928NA given as a WB-57F Canberra c/n 119 belonging to NASA. First time I have had anything at this flight level before. Wonder what it is doing in this neck of the woods (Spain). Needless to say no ADSB but Mode S of ACDD0F.
Incidentally, Airframes gives the type as a WB57 . A silhouette is required.