With its curved roof, the massive Hong Kong Aircraft Engineering Company's (Haeco) maintenance hangar resembles the main passenger terminal in style. That is not the only similarity because it, too, is a world- beater, one of the few maintenance facilities anywhere that can house three Boeing 747-sized aircraft side by side simultaneously. The complex, built by Dragages et Travaux Publics under a $1.1 billion contract from Haeco, had its own technical challenges. Not least was the cantilever roof which allows the hangar space beneath to remain column free. It was prefabricated in two halves, each weighing about 1,500 tonnes, that were then hoisted into position and supported by six masts. These masts and cable stays are attached to 1.2-metre-thick concrete shear walls that envelope the rear of the hangar. In effect, the roof is counter- balanced by the building. Raft foundations were built to guard against the effects of settlement. This is being strictly monitored. A multi-level concrete building containing workshops, stores, offices and canteen has been incorporated into the rear of the hangar. Underground, tanks for fire services, fuel and drainage have been incorporated into the design which was done by architect Llewelyn-Davies and civil and structural engineer Meinhardt. An industrial waste pre-treatment facility has been installed.