Motherships were approximately five miles in diameter. Nearly half of each ship was taken up by massive gravity-manipulating engines that allowed it to hover over a fixed point on a planet's surface as well as being able to traverse interstellar distances. During the initial tour of the New York mothership, Diana, second in command under Supreme Commander John, claimed that motherships could travel at speeds approaching the speed of light. Subsequent events, however, demonstrate that they were capable of much higher speeds.