brown wings have an 'expiry time' of twelve months and  are revoked after that period unless you keep up your 'air-time'
brown wings are an honour bestowed to a good chap who has had anal sex with a female (human)
"brown wings have an 'expiry time' of twelve months and  are revoked after that period unless you keep up your 'air-time'" What is the definition of "brown wings"?