Russia says USAF RC-135U was flying with transponder switched off

Responding to the Pentagon’s comments that a Russian Su-27 had intercepted a RC-135U in a dangerous manner, a Russian Defense Ministry spokesman said the spy plane was flying with its transponder switched off.

USAF Combat Sent
By USAF;Bburton at en.wikipedia, 2007-02-16 (original upload date) [Public domain], from Wikimedia Commons

Maj. Gen. Igor Konashenkov said the fighter flew around the American aircraft a few times to confirm that its a RC-135U and reported its tail number to ground control.

Source: Alert 5