Jakarta. Lion Air, the largest airline in Indonesia by fleet size, will ground all international and domestic flights on Friday until further notice – just five days after it resumed flying – after finding that most of its passengers have not been able to comply with the government's new Covid-19 health protocol. 

The group, which comprises budget airline Lion Air, propeller plane airline Wings Air and full-service airline Batik Air, grounded most of its planes last month after the government issued a mudik ban to prevent people from going on the Idul Fitri exodus. 

The group reopened for business on Monday but found most passengers were not able to meet health protocol requirements. 

"Many passengers had to cancel their trip because they could not show the required documents," spokesman Danang Prihantono said in a statement on Tuesday.

According to the Transportation Ministry's regulation, business trips and traveling for family emergencies are allowed as long as the passengers show documents stating they are free from the coronavirus.

They must also show a letter from their employers or documents proving the family emergencies before they can be allowed to board the plane. 

"Lion Air Group will offer full refunds to passengers who have bought tickets or help them reschedule their flights without additional costs," Danang said. 

Indonesian airlines are among businesses hardest hit by the Covid-19 pandemic.

Flag carrier Garuda Indonesia was forced this week to lay off pilots to remain afloat.

The government's large-scale social restriction (PSBB), issued to curb the spread of Covid-19, has forced millions of Indonesians to stay home for more than two months. 

Data from the Central Statistics Agency showed the number of domestic flight passengers plunged 82 percent in April to 838,100, from 4.6 million in the previous month.

The number of international flight passengers also fell 95 percent to 26,000 in April from 558,700 in March, the data showed.