Cathay Pacific is to bolster its fleet as it faces increased competition in the Asian long-haul market.
Cathay Pacific currently has 96 planes in its fleet
The Hong Kong-based carrier is acquiring 19 planes - 16 Boeing 777-300ERs and three Airbus A330-300s.
The deals, which will expand Cathay's fleet to more than 110 planes by 2010, will enable it to open more routes and develop Hong Kong as a global hub.
Cathay faces new regional competition in the shape of Oasis Hong Kong Airlines, due to launch next year.
The airline has been licensed to fly from Hong Kong to London, Cologne, Berlin, Milan and Oakland, California.
Cathay did not disclose the combined value of the transactions but analysts estimated they could be worth up to $8bn (£4.6bn).
Cathay is acquiring 12 planes directly from Boeing and seven planes on lease from the International Lease Finance Corporation.
"These aircraft orders mark an exciting and significant milestone in the development of our airline," said Cathay's chief executive Philip Chen.
"This rapid fleet increase will enhance our strength as a carrier and Hong Kong's position as a global hub and gateway to the Chinese mainland."
Aviation experts said the deal was also a boost for manufacturer Boeing in its battle with Airbus for pre-eminence in the global long-haul market.