An aircraft with a unit to transmit information on ability/inability of pilots to fly the aircraft. Guidance avionics include guidance architecture and a flight controller to fly the aircraft. The guidance architecture has two dissimilar guidance chains and a selection unit connected thereto, to the flight controller and to the unit for measuring physical ability/inability, a first guidance chain to compute a main path for the aircraft towards a destination airport based on a current state of the aircraft by following a flight plan and to compute main guidance instructions for following the main path, a second guidance chain to compute an emergency path for the aircraft towards a diversion airport based on an initial portion of the common path with the main path and to compute emergency guidance instructions for following the emergency path. The selection unit receives the main and emergency guidance instructions and transmits either one to the flight controller.