Quite a lot of sources name the Valkyrie as an extremely high lift
over drag efficient aircraft. According to Wikipedia:

"This gave the Valkyrie the best lift:drag ratio of any powered manned
aircraft ever built and allowed a much better aspect ratio on take-off
and landing. Some recent SST designs are considering this as an
option."

Anyone knows l/dmax of the XB-70? Commercial airliners are around 1:18
while motorgliders (and the U2) come close to 1:30 An L/D of 1:30
seems impossible for an aircraft like the Valkyrie?