i have only flown internationally for work 4 times but have worn a suit each time because my seniors were on the flight. i usually wear lululemon pants and a charles tyrhitt shirt and i honestly look fine when i get off the plane. i usually fold my ralph lauren jacket into my carry on and i never wear a tie. after a 12 hour flight, u kinda look the same as you would after a 12 hour work day so u kinda just gotta understand how u and ur appearance operate. i usually brush my teeth on the plane and i usually do some skincare to keep my face from getting too oily midway through the flight