The Baltic States of Estonia, Latvia, and Lithuania joined the North Atlantic Treaty Organization in 2004. These countries don't have much in the way of air assets. According to FlightGlobal.com, as of 2017, the three countries combined have three L-39 trainers, one L-410 transport, three C-27J transports, and 13 helicopters that operate either as search-and-rescue or training assets.
The NATO Baltic Air Policing Mission was established just after these countries joined NATO and is designed to protect their airspace. The mission usually consists of detachments of aircraft — four initially, but in recent years, as many as 16 aircraft have been sent for this mission — that operate out of airbases in Poland, Lithuania, and Estonia.
F-15Cs of the 32d Tactical Fighter Squadron (Image from U.S. Air Force)
On Jan. 8, the United States ended its most recent run as part of this mission. Four F-15C Eagles from the 493rd Fighter Squadron, part of the 48th Fighter Wing, were deployed to Lithuania for four months. They worked alongside F-16AM Fighting Falcons from Belgium for this mission.
These four months proved to be fairly busy, according to the Air Force Times. Russia has been aggressive with its neighbors, most notably Ukraine. Since tensions with Ukraine have heated up, NATO routinely sends two detachments. The American detachment operated out of Šiauliai International Airport in Lithuania.
Russian Air Force Su-30 (Photo from Wikimedia Commons)
While there, on at least two occasions, the American pilots intercepted Sukhoi Su-30 Flankers. These multi-role jets, assigned to the Russian Navy, flew near the airspace of the Baltic States. The U.S. Air Force F-15s were scrambled in response to intercept them. These encounters were caught on tape.
You can see these encounters on the video below. One thing you won't see are the types of buzzing stunts that Russia has pulled on American ships and planes in the past.