Disclosed are aircraft configured to perform tethered and untethered flights as well as methods of operating such aircraft. During a tethered flight, the aircraft is connected to a power line using its connecting module. While tethered, the aircraft can receive electrical energy from the power line and use this energy for propulsion and/or storage. The aircraft comprises a propulsion module for providing vertical and horizontal thrusts. In some examples, the aircraft comprises a transport module. The transport module may be removably attached to the propulsion module and be replaceable with another transportation module. During an untethered flight, the electrical energy is supplied to the propulsion module from a battery and/or a generator on board of the aircraft. The untethered flight capability can be used for landing and takeoff, flying away from power lines or when the power line is not operational, and other like examples.