A gas turbine engine (10) includes a first fire zone (Zone 3) in the region of a core of the engine and a second fire zone (Zone 1) in the region of a fan case of the engine, the first and second fire zones being separated by fire walls. The first fire zone is located generally radially inwardly of the second fire zone but includes a bifurcation part which extends radially outwardly of the remainder of the zone for limited circumferential extent. The engine further includes a disconnect panel (52) mounted on the fan case (32) to extend radially outwardly therefrom, the disconnect panel (52) forming a fire wall and providing means for pipes and harnesses (44) to be routed therethrough.