Four small airlines in Indonesia have been grounded after failing to pass the country's quarterly safety audit of air operators.

Various news reports quote Indonesia's Ministry of Transportation as saying Pua Wisata Baruna, Sampoerna Air Nusantara, Dabi Air Nusantara and Atlas Deltasatya have been grounded after failing the quarterly safety audit.

All are small and relatively unknown airlines that operate mostly domestic charter flights.

Indonesia has been having quarterly safety audits of air operators in an effort to improve air safety.

Airlines that fall into the lowest category automatically have their air operator certificates (AOCs) suspended but the carriers can apply to have their AOCs reinstated.

Source: Air Transport Intelligence news