The plane's tail number, 62-4131, was tracked as it flew over the territory of the United States less than 24 hours ago, according to the website planefinder.net.
The aircraft reportedly conducted a 10-hour observation flight at an altitude of more than 10,000 meters, during which the plane could be seen flying near the Russian border for a least two hours.
The Tuesday flyover is the latest in a series of incidents with the RC-135 aircraft and Russian warplanes in the Baltic Sea in the past few weeks.
Late last month, Pentagon officials claimed that the Russian fighter jet Su-27 allegedly performed a "barrel roll" within about 24 feet of a US Air Force RC-135 reconnaissance plane.
For his part, Russian Defense Ministry spokesperson Igor Konashenkov denied similar allegations from a separate incident earlier in April.
"The reports of foreign media saying that a Russian Su-27 allegedly flew in dangerously close proximity to a US RC-135 reconnaissance aircraft in the skies over the Baltic Sea on April 14 are not true," he said.
