I almost always start the job with researching and collecting references. Looking at them helps to feel the atmosphere of the era and you will see clearly the hairstyle and clothing or other props that can add to the character. In this case the blue line drawing on the left is the first sketch based on a real British fighter's vintage photo. He is wearing a pullover with a unbuttoned jumpsuit. His carefully trimmed mustache is very stylish. I made his face more characteristic, slightly based on another, contemporary pilot's features. Although I liked his natural and confident look he was not what I was looking for. I was drawing him because I thought his study would help me to create the fictional pilot for the game. To get that look some exaggerations needed.
Admitting (after a satisfying first sketch or study) that your second approach is a failure is not easy. The smallest, light brown sketch (only lines, no blocking) shows an abandoned version where I was going to the wrong direction. I drew it over the first sketch, but now our hero is wearing a uniform. Unfortunately his posture is not specific enough, his facial features are way too general and his body type is average. It is a good example for a bad design. :) He is so uninteresting and somehow rigid the best we can do is just let it go and start all over.
It is always good to make thumbnails with loose sleekly straight and curvy lines. Draw the spine, a kind of simplified skeleton of the guy. To get the character anatomically correct I use my other references sometimes 2-6 photos to get the right posture. Family members or friends have to pose when there is no other way to get it right. There is no detailed rendering that can fix the wrong or uninteresting posture.
Since the aim was to provide not an artistic or lifelike, but a rather game-fitting guy I started to play with the proportions. Simplifying the lines I was looking to find his posture keeping in mind it should suggest confidence with some hint of easygoing attitude but somewhat arrogance too. He knows he is good looking and after dozens of fights, shooting others and being almost killed he sees the world with different eyes. He does not give a damn about what Mr X thinks of him. On the other hand, he is not cynical, but rather smart and charming with some dry humor sense. So I broadened his shoulders and slimmed his waist. Not only he got and almost sculpted hairstyle, but his jawline got more square like and his chin came forward.
I love rendering and get carried away easily by colouring or refining details, so I worked only with values as you see it in the brownish blocked image in the middle.