Kai Tak Tunnel, formerly known as the Airport Tunnel, is a tunnel in New Kowloon, Hong Kong, which connects the Kowloon Bay and Ma Tau Kok areas by going beneath the former Hong Kong International Airport (Kai Tak Airport). It is part of Route 5.
The tunnel provides a quick link between the two ends of the tunnel, as before the construction of the tunnel vehicles had to detour through Kowloon City to reach the other end. Kai Tak Tunnel is currently managed by Greater Lucky (H.K.) Company Limited.
Construction of the tunnel had started by 1975,but because of the difficulties in digging under the airport runway, it was not complete until 1982. The southern tube opened to two-way traffic at 3:00 pm on 29 June 1982. The second (northern) tube opened on 8 October that year. The Airport Tunnel was the first tunnel in Hong Kong to be toll-free, excluding short underpasses.
With Kai Tak Airport's shutdown in 1998, the Airport Tunnel was no longer fulfilled to its name. The Hong Kong Government announced to rename to Kai Tak Tunnel on 2 March 2006 that the tunnel, effective from 4 May 2006, after several years of consultation with groups including the Kowloon City District Council. The name was changed to commemorate the former Kai Tak International Airport.
The tunnel consists of a pair of tubes of about 7 metres diameter each, 1.26 km long.