An aircraft (2) comprises at least first and second gas turbine engines (10a, 10b) arranged in a line extending generally normally to an aircraft longitudinal axis (A), each engine (10a, 10b) comprising at least one compressor or turbine rotor disc (32-42) defining a respective rotational plane (D32-D42). The rotational plane (D32-D42) of at least one of the rotors (32-42) of at least one of the engines (10a, 10b) is angled relative to the aircraft longitudinal line (A) such that a burst disc plane of the respective engine (10a, 10b) is nonintersecting with another engine (10a, 10b).