This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time This model uses a single rotor to stay up in the air. It resembles a remote-control helicopter that can stay in the air for a long time