From an interviewer's point of view...
Be clean and smart; there's no need to look like a car salesperson, but don't be scruffy either. If you're male, have a haircut, and shave. If you're female remember you are going for an engineering job, not a receptionist job, and dress accordingly. If anyone tells you these things aren't important, ignore him/her. Impressions count.
Bone up on Monarch; know its outline history and all about its current operation and fleet. Even key names. If you're not interested in the company, they will lose interest in you.
Be very clear about why you want to join the scheme and what your short, medium and long-term goals are. They want motivated people. You must work this one out before you get there; if you're making it up as you go along it will be obvious that you are.
When asked a question, think for a second or two and give a concise answer to the question. Stop when you've finished it! (Sounds obvious but many people feel a need to ramble on.)
In the group situations, only say or do something that's useful and helpful to the team goal. If the others defer to you, take charge. Don't try to seize control by force; you'll come across as a bully. But if there is a real vacuum, fill it. You must attract the assessors' attention positively.
Be yourself.