Ace Mason is an agent with the Flying Secret Service.
First about the organization, we are told very little; it is run by a mature man with short, white, receding hair who is referred to as Mason's Chief and once, in the first recorded adventure, as head of the "Intelligence Bureau". From that we can only surmise that the Flying Secret Service is part of that umbrella. Well, studying the pictures a bit closer we see that this director is wearing a military uniform so this bureau likely is a part of the Department of War (this adventure taking place before the department name change).
The timeframe for the two adventures we have of Ace Mason is about a year after the start of the Second World War but before America was attacked and still strived for neutrality. Interestingly, the two threats that Mason will have to combat to keep the country safe single-handedly will come not from any of the Axis powers but from two individuals, one foreign and one domestic, who want to cause considerable trouble for America. The foreign enemy wants power while the domestic one wants revenge. Both are scientists by vocation.
Logan is shown to be a tall, slender, muscular man with impressive athletic abilities, shown when he does aerial acrobatics while riding a giant condor (second adventure, see for yourself). He is certainly an officer in the Army Air Corps though his rank is never mentioned. His age is also not stated but it would be be close to 30 years old. He is an accomplished fighter pilot and quite at home in the air regardless of his vehicle of choice.
Mason has a young friend, barely of legal age, named Stubby Logan who has the position of gunner on the aircraft that Mason flies but is more of a sounding board than anything else - okay, he does come to rescue Mason in the first story so he is not only a trained pilot himself, he is a loyal friend. Well, he must also have one other skill because Mason at one point puts his plane on automatic pilot and radios Stubby to 'guide her back' and then apparently land it remotely.