Kowloon was developed largely in the 20th century, after Kowloon Wharf and Kowloon-Canton Railway were built. Airplanes used to fly above Kowloon to and from Kai Tak Airport until 1998, so buildings there are usually lower than the ones on Hong Kong Island because they had height restrictions. The height restrictions were lifted after the opening of the new Hong Kong International Airport in 1998.