Tickets will be distributed to travellers next year.
Cheng said they were purchased to support Hong Kong airlines during the pandemic.
However, many major airlines have struggled to return to pre-pandemic flight schedules, including those that fly to and from Hong Kong.
This is partly due to the pandemic but the Ukraine war has also caused difficulties.
Russia's invasion of Ukraine resulted in the closure of Russian airspace, making it difficult or impossible for many airlines to fly their regular routes.
British airline Virgin Atlantic recently announced the closure of its Hong Kong office and said it would no longer fly to the city due to issues related to the Ukraine war. This ends 30 years of flying between London Heathrow and Hong Kong.
"Significant operational complexities due to the ongoing Russian airspace closure have contributed to the commercial decision not to resume flights in March 2023 as planned", the company said.
Hong Kong also earned a reputation for having some of the toughest Covid-19 rules as it pursued a zero Covid approach.
However, last month the government dropped pre-departure tests and hotel quarantine for arrivals, which saw a surge in sales for flight tickets in and out of the country.
According to Prudence Lai, who works as a senior analyst at market research firm Euromonitor International, free air tickets will help Hong Kong rebuild its reputation amongst travellers.
"The pre-Covid status of Hong Kong represents the market potential of a full recovery," she told the BBC.
"However, this is highly dependent on when mainland Chinese tourists will return, as mainland China contributes to more than half of Hong Kong's inbound arrivals and travel receipts."
Hong Kong welcomed 184,000 visitors between January and September this year; a severe drop compared to pre-pandemic. In 2019, 56 million people visited.
