NATO’s fighter jets policing Baltic airspace were scrambled six times last week to identify and escort Russian military aircraft in international airspace over the Baltic Sea, the Lithuanian Defense Ministry said on Monday.

On Monday, Sept. 16, a Beriev A-50 reconnaissance aircraft and two Sukhoi Su-27 fighter jets were intercepted en route from Mainland Russia to the Baltic Sea exclave of Kaliningrad.

On Tuesday, Sept, 17, the alliance’s aircraft intercepted two Tupolev Tu-160 bombers and two Sukhoi Su-27 fighters flying from mainland Russia to the Baltic Sea and then back. Later on the same day, NATO’s jets intercepted two Tupolev Tu-160s on their way back to mainland Russia.

A Beriev A-50 plane was intercepted on Wednesday, Sept. 18 as it flew from Kaliningrad to mainland Russia. An Antonov An-12 transport plane flying from the exclave to mainland Russia was intercepted on Thursday, Sept. 19.

NATO’s jets were scrambled over a Sukhoi Su-30 fighter on Friday, Sept. 20.

In many cases, Russia’s military aircraft submitted no flight plans, flew with their onboard transponders switched off, and did not keep radio contract with the regional air traffic control center.