Once dominated by startups, the emerging air taxi industry has attracted the attention of traditional aerospace companies that have invested millions of dollars. Some have also begun working on their own concepts for these small, electric passenger aircraft. Even if AAM never achieves the billion- or trillion-dollar annual valuations predicted by analysts, Glenn McDonald and Martha Neubauer of the AeroDynamic Advisory consulting firm believe the Airbuses and Boeings will still reap the benefits.