In particular, on September 21, NATO fighters were scrambled to identify and escort an Il-20 aircraft flying from mainland Russia to the Kaliningrad region without a previously filed flight plan, with its onboard transponder turned off, but maintaining radio communication with the regional air traffic control center. On September 22, NATO fighters were dispatched to intercept two Su-30 aircraft flying from the Kaliningrad region and back through international airspace. Their onboard transponders were turned off, the crews did not file flight plans in advance, and they did not maintain radio communication. On September 24, NATO fighters identified and escorted three MiG-31 aircraft, one Tu-134, one Su-30SM, and three Su-30M2s. The aircraft were flying through international airspace from the Kaliningrad region to mainland Russia. They had not filed flight plans in advance, the crews maintained radio communication, but kept their onboard transponders turned off. On the same day, NATO fighters detected and escorted one Su-35, two Su-30M2s, and one Il-20 flying from the Kaliningrad region and back through international airspace. Their onboard transponders were turned off, the crews did not file flight plans in advance, and they did not maintain radio communication. On September 26, NATO fighters intercepted one Su-24 aircraft flying from the Kaliningrad region and back through international airspace. It had not filed a flight plan in advance, its onboard transponder was turned off, and the crew did not maintain radio communication with the regional air traffic control center.
