The Hong Kong government gave final approval for a third runway at the Asian financial centre's airport, aiming to meet surging growth in passengers and air cargo.

Officials said the project will begin next year and cost 141.5 billion Hong Kong dollars ($A23.81 billion).

About 650 hectares of land will be reclaimed from the sea for the runway and a new passenger building. Construction is expected to be completed by 2023.

Hong Kong’s airport expects to reach maximum capacity under its current layout by 2022 at the latest.

Across Asia, airport operators are scrambling to build new terminals or expand existing ones to keep up with growth in air travel.