Recently a new Mode-S hex code AE0542 has popped up/ This hex code definitely looks like a KC-135 tanker based on call signs and boy has this hex code used a wide variety of Mode-S call signs since 1 Oct 2016.
What call signs you ask?
Arius 21
CETUS 21
Cabal 31
Happy 63
Kanza 01/71/81
Snap 83/90/92
Spur 91
Turbo 13/78/81
This one has me scratching my head and if anyone gets a serial number tie up for the airframe, please drop me a note.