The number of dedicated flights under the agreement may change depending on the coronavirus situation in the cities, Yau said at a briefing Tuesday, without elaborating. The two governments are still working on the details of the plan, including the start date.

Singapore and Hong Kong said on Oct. 15 they planned to open their borders to one another for the first time in almost seven months, with quarantine replaced by coronavirus testing. Singapore’s Transport Minister Ong Ye Kung said at the time that he hoped the bubble would start in weeks. Travelers must have been in Hong Kong or Singapore for 14 days before departure and will need to take mutually recognized Covid-19 tests.

Governments around the world have been trying to create travel bubbles to help revive their economies and aviation industries. Opening links is particularly important for places such as Hong Kong and Singapore because they rely so much on international connectivity and business.

Cathay Pacific Airways Ltd.’s shares fell 1.4% Tuesday, their first loss in four trading days, while Singapore Airlines Ltd.’s slipped 0.3%.