Pentagon to protest “unsafe and unprofessional” intercept by Russian Su-27

On Apr. 7, a U.S. RC-135U flying over the Baltic Sea was intercepted by a Russian Su-27 in “an unsafe and unprofessional manner.”

A Russian Air Force Su-27 Sukhois aircraft intercepts a simulated hijacked aircraft, foreground, during Vigilant Eagle 2013 at Joint Base Elmendorf-Richardson, Alaska, Aug. 27, 2013 130827-F-XT249-155
By TSgt Jason Robertson [Public domain], via Wikimedia Commons

Not much of the encounter is known except that the fighter came within 20 feet of the spy plane.

Source: Alert 5