Legislators yesterday approved funding for a $105 million air-traffic-control radar to be installed in 2003. The system's installation will take about four months, during which time flights at Chek Lap Kok will have to rely on a less powerful back-up system. Director of Civil Aviation Albert Lam Kwong-yu said that radar may not be able to detect unidentified aircraft or planes without transponders, which allow them to communicate with other planes and controllers. He said potential users of Hong Kong airspace would be notified to take care. While safety levels might decline during installation, the system was overdue for replacement, he said. Legislators also approved $50.7 million in funds to improve systems to cope with the increasing complexity of plane movements around Hong Kong and the Pearl River Delta.