So my info may be out of date, but when I interviewed in 2018 the group exercise was 8 candidates around a table with a pack of info (each subtly different) given 30 mins to make a decision on what to do with a BA route to a fictional carribean island - change aircraft, add frequency, pull out all together etc. 5 mins before time there's a. "Urgent email just come in". Obviously it's not about the decision (although its a good idea to decide something!) its about how you work together.
Interview was with a BA pilot & HR person. 50/50 split between "give an example of a time when..." questions and CV walk through and company knowledge.
The rest of the aptitude tests etc I think have changed so I doubt I could give any useful information.
Hopefully this might get you started until someone else can give you more accurate info.