Wheels Up—a New York–based air-taxi service that offers membership for private air travel—has teamed up with Four Hundred, a concierge company that coordinates access to restaurants, sporting events, concerts, and other experiences around the world. In the 8760 Concierge by Four Hundred program, a team of “personal lifestyle specialists,” as Four Hundred calls them, will be available 24/7 to fulfill travelers’ requests for such items as tickets to the hottest Broadway shows, tables at top Las Vegas restaurants…