"Illustrious" carried out two weeks of fixed wing flying serials exercises in the North Sea off Hartlepool in March 2007, during which seven GR9 Harriers from No. 4 Squadron RAF, Joint Force Harrier touched down on her flight-deck. Also during these exercises, seven of her crew had to be airlifted to hospital in Middlesbrough on 13 March suffering from fume inhalation and throat and eye irritation after an accident with chemicals in cleaning a junior ratings' toilet area. "Illustrious" sailed on to Portsmouth, where they rejoined her on leaving hospital.