To everyone going to the assessment with Aer Lingus:
I was lucky enough to attend the assessment earlier this year, however, unsuccessful, I was still advanced all the way to the last step, which was the simulator assessment.
Basically the first order is an introduction to the company, profile, supply and demand, future plans, and hiring strategy etc.
After that, you are grouped into 5-6 people and given a task with a set of rules. Our task, was to build a Lego toy in a certain amount of time, and the group finishing first would be given extra bonus points - task was to end with the most points.
We were given x amount of points, which could be used to "buy" instructions, be it video, manual and so on.
You could choose to spend all points and buy all the aids and try to finish first for bonus points, or you could save the points, use longer time to build the toy and have more points in the end, if you finish first of course. The whole point, obviously as someone pointed out was not to "win", I assume they would rather look into how you work as a group and your individual contribution towards the completion of the task.
After the group exercise, for those successful would advance further to the panel interview, which consisted for us, of 4 candidates and 2 assessors. They would give us questions, discussion topics (example question we were given: how do you think supersonic transport contributed to the industry and do you think we would ever see supersonic transport again, why and why not, etc.) They wanted us to come to a conclusion as a group for the given statement/problem and each member were given a topic which had to be started and then concluded.
I personally think that they wanted to see how you were able to formulate your opinions and ability to discuss with others, while also analyzing how dominant or subservient you formed your opinions in a group discussion environment.
If successful, candidates would advance to individual interview, by a HR and flight crew representative. They are really nice and easy-going, nothing too direct and strict, at least in my experience. They ask you flight operation related questions and mostly scenario-based.
If successful, candidates would advance to the simulator assessment - which were pretty straight-forward. First scenario, all-engines operating departure, followed by airwork (steep turns, rolling out on specific headings, speed changes, altitude changes etc.) basic stuff. Then one ILS approach into Dublin - end of scenario.
Second scenario, one-engine-inoperative departure, engine failure after v1 - vectors for ILS with FD - end of scenario. Third scenario - one crosswind ILS approach and landing (10-15kts xwc I would say). All in all pretty straight forward and the assessor is really nice and calm.
Obviously, your experience might differ from mine, but this is how mine was.
Sorry for the long post - hope this helps!
Good luck and happy trails