A high density air corridor is expected to be an air space where aircraft capable of airborne self-separation are allowed to fly into the same direction. A self-separation algorithm in a high density air corridor that is feasible for the human pilot manual control is discussed in this study. In addition, the corridor width limitation is also considered to definitely prevent any conflict against the aircraft outside the corridor. Through a series of the traffic simulation, it has been clarified that an algorithm that indicates the fixed heading change to the pilot is able to achieve a safe corridor operation in combination with flight speed control. It is also clarified that the information of the intended flight speed and the collaborative separation control are indispensable for the air corridor efficient operation.