The incident took place on 13th February, when jets from Kaliningrad were detected. The flight plan for this sortie was never filed, while the aircraft had no transponders turned on, and thus they were not visible to the civil air traffic and ATC. Furthermore, they were headed toward the Polish Area of Responsibility within the NATO system.
This has been the first QRA scramble of the RNLAF F-35A Lightning II. Two jets took off in a few minutes and intercepted the threat - three Russian aircraft. These were two Su-27 Flankers armed with the R-73 missiles, escorting the Il-20M SIGINT platform. The formation was flying over international waters, alongside the northern limits of the Polish airspace.
The RNLAF jets were escorting the Russian aircraft remaining at a safe distance until the formation transitioned to AoR of another NATO member state. This refers to Germany that scrambled its Eurofighter jets to watch the moves of the Russian aircraft. The mission flown by the Russian jets, apart from being a show of force, also serves the purpose of collecting data on NATO operations. The Il-20M is a frequent sight over the Baltic Sea region.
The Il-20M is one of the more obscure variants of the turboprop Il-18 airliner. It is used to carry out reconnaissance sorties in areas close to the borders. This is possible thanks to the SIGINT and RADINT equipment installed onboard, including the hardware that enables the crew to intercept VHF radio chatter, Igla side-looking radar underneath the fuselage, along with photo-cameras. Il-20 aircraft have gone through several upgrade programmes, without any successor being developed.