Brussels Airlines is the current national carrier of Belgium. It has undegone a lot of changes. When the long time Belgian national carrier Sabena went bankrupt, a new airline was created with the name SN Brussels Airlines. SN was the flight code of Sabena. SN Brussels Airlines and Virgin Express then merged and the end result is the present Brussels Airlines. Currently Brussels Airlines is 100% owned by SN Airholding SA/NV which in turn is 100% owned by Lufthansa.

OO-SND is an Airbus A320 version 200 which was delivered to LTU in 2002. It then flew for Air Berlin until Air Berlin's bankruptcy in 2012 and since that for Brussels Airlines. It has had different special liveries. This current colouring is called Belgian Icons - The Smurfs and the plane has been given the name Aerosmurfs.
Picture from Rome Fiumicino airport 16.3.2019 by Markku Salo.

OO-SSS of SN Brussels Airlines is an Airbus A319 and it is again in a totally different livery.
Picture from Madrid Barajas airport 12.6.2023 by Ilkka Siissalo.

OO-DWA of SN Brussels Airlines is an Avro RJ-100. It was delivered to DAT in 1997 and DAT used it to run on routes of the then bankrupt Sabena. When Brussels Airlines was established as a company as a successor of Sabena, the machine moved there. It worked for Brussels until the summer of 2017, when it was sold to AeroFlight. It is reported to be only "stored" after the summer of 2017.
Picture from Oslo Gardermoen airport 1.9.2016 by Ilkka Siissalo.