1) Airlines are exempt from the NRLA by being covered by the RLA, 2) The question makes it appear you are not currently employed by an airline, as such, would not be protected by any federal protection for union membership, and 3) as the question makes it appear you are not currently employed by an airline, as an applicant, the potential employer holds all the cars except where it comes to a protected characteristics covered by discrimination laws. You have much to learn if employment for a corporation is in your future regarding applicant/employee/employer relations, and the regulatory rules that govern/do not govern them.