The NC-135W is a test-bed aircraft added to the Air Force Material Command's 645th Material Squadron/ Det. 2, and is mainly used by L3 Technologies at Major Field near Greenville (TX).
61-2666 has been modified as an NC-135W to test systems and equipment used on RC-135V/ W Rivet Joint reconnaissance aircraft.
Whenever visiting or transiting Europe in the past, the NC-135W mostly used the callsign "Same-40". At this moment it is not known if it will use Mildenhall as a temporary base, or that it will move on to, for example, Souda Air Base on the isle of Crete. Normally, both Mildenhall and Souda, have one or two forward detached RC-135V/W Rivet Joint aircraft from the 55th Wing based at Offutt AFB (NE).