Exchanging payloads between multiple vehicles is a challenging problem that finds applications in sustained monitoring and long-range payload transportation. In this paper, we take the problem one step further and explore the design and implementation of a system of aerial vehicles that can exchange a small cargo/payload while air-borne. The proposed approach exploits the hover-capabilities of multirotor vehicles, and works within the constraints and the challenges imposed by such a task (such as proximity and contact forces). It is also portable to a wide range of vehicles, and does not require custom flight maneuvers in order to be viable. A simulation framework is utilized to highlight the key challenges addressed by the system. We present detailed results from experiments conducted outdoors that demonstrate two vehicles exchanging a small 60 g payload unit between them.