In order to join the Academy you need to be legally in the US and authorized to study. A current US Passport or US Birth Certificate is required, or if a foreign Citizen, a Permanent Resident card or a Visa that allows study.
Foreign Citizens require a quick TSA background check approval (normally takes 2 weeks).
At our San Diego, CA (KSEE) location we are able to issue I-20's to International Students that go towards the issuance of an M-1 Student Visa.
More here: https://www.slingpilotacademy.com/prerequisites/