As a male applicant I would wear a suit but with a casual smart shirt that if needed would work with a tie, as said easyJet are a very relaxed company and if you manage to visit their HQ you will see most staff in Jeans and t shirts some in shirt and trousers but not a tie insight. The new big boss Andy Harrison is currently wearing full cabin crew uniform at work to see if its any good and made the point the best way to see how it looks/feels is to wear it himself for a few months (proving to be possibly a good boss fingers crossed). If on the day most have ties on, wear it! if not put it away in your bag/pocket. The main thing is be smart and tidy clean shoes, brushed hair, clean fingernails and a good shave... good luck it’s a fun company