There is no single answer and no Airline or Airport is the same. So for your BA T5 example, there are many systems and vendors involved that could contribute to a failure or degradation of service ranging from in-house developed software, vendor departure control systems & Airport infrastructure. And all these normally have to talk to each other in one way or another.
SITA still provides services however, i’m not sure they would be running on the T5 sets as they are mainly only used by BA and dont require other Airline usage. Saying that though, SITA more than likely involved somewhere at some point.
Last edited by nuisance79; 5th Apr 2022 at 19:19.