The United States and Cuba have reached an understanding on resuming regular commercial flights between the two countries, Cuban and American officials said on December 16.

It is unclear when the flights would start because negotiations between the Cuban government and the US airlines could take months.

The move is a significant step nearly a year after the US and Cuba began restoring diplomatic relations.

The US reopened its embassy in Havana in August after a 54-year absence.

A State department spokesperson said the two countries “are making progress but still negotiating” on resuming flights.

The understanding is a key development as Cuba and the US continue to negotiate over a number of issues which could ultimately see the US trade embargo lifted.

The news comes as travel between the US and Cuba surged by an estimated 50% this year.

Thousands of Americans are already visiting Cuba and hotels and hostels are booked for months.

However, those traveling have to do so using difficult to book charter flights or via third countries.

A formal agreement could mean more than a dozen flights arriving into Cuba from the US a day, officials said.