It was the first time the International Air Transport Association's Travel Pass initiative was used by travelers on a Europe-bound flight, the airline said in a statement.

It had earlier been used on a Tokyo-bound flight on August 12.

Both trial runs showed positive results, potentially paving the way for a resumption of regular international flights.

The trial will continue in September, including on a flight to Seoul on September 12 and to Tokyo on September 21.

Travel Pass, which allows people to store verified Covid-19 certificates on a smartphone app, has been adopted by more than 70 airlines globally.

Passengers have to register on the IATA website at least three days before departure, download the Travel Pass application in their phone, create their digital health passport, and enter their flight information.

During the trial phase, passengers have to furnish hard copies if demanded by authorities.

EU members rolled out digital health passports in July as part of efforts to gradually ease travel restrictions within the bloc, including for non-EU passengers.

Vietnam closed its borders and canceled all international flights in March last year.

Vietnam Airlines last July resumed commercial flights from Hanoi and HCMC to Australia and several Asian and European destinations.