An aircraft 1 in the form of an aeroplane with a spiral inducing assembly 2 which is capable of inducing the aeroplane to travel in a continuous spiralling motion without rolling. Two fins 3 and 4 are attached to a tube 5 that is able to rotate around the encircled part of the fuselage. The fins 3, 4 are able to rotate in a pivoting manner on the rotatable tube 5 with respect to the rotatable tube 5, thereby changing their pitch relative to the longitudinal axis of the rotatable tube 5. Fin 3 is larger than fin 4. The diferene in sizes between the fins makes the larger fin 3 exert a greater force on the rotatable tube 4 than the smaller fin 4 when the fins are pitched in unison. The aerodynamic imbalance between the fins thus casues the rotatable tube 5 to rotate. When pitched at an angle to the longitudinal axis in unison, both fins 3, 4 would exert a lateral force on the rotatable tube 5. Thus, as well as forcing the rotatable tube 5 to rotate, the fins 3, 4 would also push the rotatable tube sideways. But as the rotatable tube is pushed sideways, it rotates, and hence the lateral direction of push constantly revolves, causing a spiralling motion when in flight.