The disclosure relates to a vertical take-off and landing, VTOL, flying machine. The machine includes a ducted fan having an intake side and an outlet side, at least two co-axial rotors configured to contra-rotate about a fan axis X when driven in rotation; a primary drive source arranged substantially co-axially with the ducted fan and to the outlet side of the ducted fan; and first and second thrust air ducts configured to split thrust from the ducted fan into a pair of thrust streams and to guide the two respective thrust streams to opposite respective sides of the primary drive source, the ducts being rotatable to direct motion of the machine. A number of configurations of secondary drive sources and alternative thrust sources are provided for improved safety.