The bridge loan was part of a $5 billion rescue package led by the Hong Kong government and Cathay's major shareholders Swire Pacific Ltd and Air China Ltd last year to help the airline weather the COVID-19 crisis.
Cathay Chief Executive Augustus Tang said in a statement the airline had not yet drawn down on the loan as it adopted a suite of measures to save cash, but the extension would give it more flexibility to manage its liquidity position.
Cathay had HK$28 billion of liquidity as of December 2020 and also raised HK$6.74 billion from a convertible bond issue in February and $650 million in a bond issue last month.
The airline's move to access as much liquidity as possible at a time when passenger numbers are down by more than 99% from 2019 levels follows a decision by rival Singapore Airlines Ltd last month to issue S$6.2 billion ($4.69 billion) of convertible bonds.
The Singapore Airlines convertible bonds, underwritten by majority shareholder Temasek Holdings, were an optional part of a state investor-led S$15 billion rescue package announced last year.
Both airlines lack domestic markets at a time when international borders are still largely shut.
($1 = 7.7591 Hong Kong dollars)
($1 = 1.3224 Singapore dollars)
(Reporting by Jamie Freed in Sydney; Editing by Muralikumar Anantharaman)