thank you all for the comments,I very much appreciate them.
I originally designed the suit to be very much in line with a military flight suit. I thought that Hal being in the military, when he got the ring and first took to the skies he would construct something that he knew or was at least familiar to him. I don't think he would create something to alien, he would go with his gut and after all those years in the military his uniform design would just come from his subconscious. So I started off with what ended up feeling like a green air force flight suit, then I thought what are the things Hal would get rid off if he didn't have to physically put it on, so zips and press studs/Velcro all went then I just tried to simplify it down to it's key elements and the only real nod to his military flight suit is his open collar with the white tee underneath.