This particular fella comes from the dawn of the Golden Age of Superheroes, back when "a dude who can fly" was a bankable concept in and of itself. If you had that angle locked down, you really didn't need extraneous clutter...
...which in the Black Condor's case included "pants" and "a shirt."
Condor's minimalist choice of fighting togs can be traced back to the character's origins as an avian-themed riff on Tarzan's pulp adventures. After his archaeologist parents were slain by bandits, the infant mystery-man-to-be was taken in and raised by a colony of "intelligent" condors.
There the young man learned the language, mysteries, and (presumably) carrion-munching ways of his feathered foster brethren. Getting the hang of flying was a little bit trickier...
...but nothing that a few panels and some heavy suspension of disbelief couldn't solve.
Once that was sorted, it only took a little anti-bandit payback, an encounter with a kindly monk, and the assumption of a dead senator's identity to get him back to America and battling Ratzis and gangsters on a monthly basis.
Since those heady logic-optional times, Black Condor has undergone multiple minor retcons and spun off a pair of legacy characters -- all adding additional baggage and superfluous explanations to what was a delightfully uncomplicated concept.
I first encountered the character during the "Crisis on Earth-X" arc in All-Star Squadron, where Roy Thomas and Rick Hoberg attempted to flesh-out the backstory of the Quality Comics alt-corner of DC's multiverse (while offing the Red Bee in the process). I've since read through Condor's Eisner/Fine-helmed adventures in Crack Comics, which are pretty amazing -- like so many early Golden Age superhero features -- for witnessing the foundations of the genre get hashed out in real-time.
Honestly, though, no story the Black Condor has appeared in can match the Jerry Ordway illustration of that Who's Who entry above. It perfectly captures the square-jawed, high concept essence of the character in all his elegant pulp-inflected simplicity...
...even with the garish, off-register "Flexographic" printing muddling up Ordway's stellar artwork.