what is there to hide?
I may be wrong but don't you have to 'openly declare' that you are a mason if you are a serving member of HM services??
It is this rule/restriction has 'stopped' many servicemen joining whilst they are still serving. Those lodges which are service connected are having fewer joining at the moment as now most are waiting until they retire.
I do not think there are high numbers of masons in the flying game anyway.