As razões pelas quais tais aeronaves (incluindo Spirit of St.Louis, como apontado por @ymb) foram autorizadas a voar, são explicadas em outra resposta . Citando isso:
You don't need a panoramic view to land, ... Navigation is easy enough through side windows ... and you can just yaw the plane left and right for the times you do want to line up with something.
Even today, tail draggers have basically zero forward visibility on the ground so they taxi by watching the edge of the pavement with the occasional sharp s-turn to check ahead.
Quanto aos requisitos de certificação, você pode obter um certificado experimental e reproduzi-lo. FAA emite certificados experimentais para aeronaves de competição :
§21.191 Experimental certificates.
Experimental certificates are issued for the following purposes:
(e) Air racing. Participating in air races, including (for such participants) practicing for such air races and flying to and from racing events.
O GeeBee R2 estava voando tão recentemente quanto 2001 (não isso recente, eu sei), então eu tenho certeza que alguém pode voar se eles o estiverem usando. A FAA requer autorização de piloto especial para este tipo de aeronave:
What type of experimental aircraft requires an FAA issued authorization?
This information applies to pilots of aircraft to which the FAA has issued Special Airworthiness Certificates for the purpose of Experimental under Title 14 CFR section 21.191 and are one of the following:
"Large" aircraft (more than 12,500 pounds),
Turbojet powered, or
Airplanes that have a VNE (never exceed speed) in excess of 250 KIAS and more than 800 HP.
