The paper proposes EverCopter, which provides continuous and adaptive over-the-air sensing with detachable wired flying objects. While a major advantage of sensing systems with battery-operated MAVs is a wide sensing coverage, sensing time is limited due to its limited amount of energy. We propose dynamically rechargeable flying objects, called EverCopter. EverCopter achieves both long sensing time and wide sensing coverage by the following two characteristics. First, multiple EverCopters can be tied in a row by power supply cables. Since the root EverCopter in a row is connected to DC power supply on the ground, each EverCopter can fly without battery. This makes their sensing time forever, unless the power supply on the ground fails. Second, the leaf EverCopter can detach itself from the row in order to enjoy wider sensing coverage. An EverCopter, while it is detached, runs with its own battery-supplied energy. When the remaining energy becomes low, it flies back to the row to recharge the battery.