The Hong Kong-based airline told the stock exchange it had purchased the A350-900 planes with "significant price concessions" from the manufacturer, for delivery between 2016 and 2017.
"It is normal business practice of the global airline industry to disclose the aircraft basic price, instead of the actual price, for aircraft acquisitions," it said, putting the basic price at US$1.63 billion.
The company will fund the transaction with commercial bank loans, other debt instruments and internal cash resources, it added.
"The Airbus aircraft will replenish and expand the fleet capacity of the company," it said.
"The company expects that the Airbus aircraft will deliver improved payload range capability at competitive operating costs whilst providing high standards of passenger comfort and safety."
Cathay shares were up 1.8 percent at HK$14.66 in mid-afternoon trade.