On April 17, Indonesia pledged to shut down airlines that persisted to flout safety markers, as the United States advised its citizens not to fly on the nation's airlines after a recent spate of accidents.

In a message sent to U.S. citizens in Indonesia, the American embassy cited an audit by the Indonesian civil aviation agency, which revealed that no local airline was in excellent condition.

It also said "serious concerns" over air safety had led the U.S. Federal Aviation Administration (FAA) to downgrade Indonesia's safety oversight category from 1 to 2 indicating it was not meeting International Civil Aviation Organization (ICAO) standards.

"Whenever possible, Americans travelling to and from Indonesia should fly directly to their destinations on international carriers from countries whose civil aviation authorities meet international aviation safety standards," the embassy said.

The Indonesian audit of 54 aviation firms last month revealed none made it to the first of three rating classes, while six were given a warning to comply with safety regulations in three months or face closure.

"After three months when they've not improved then we close them," Transport Minister Hatta Radjasa told foreign journalists, referring to the airlines on closure warning -- Adam Air, Kartika Airlines, Jatayu, Batavia, Trans Wisata Air and Dirgantara.

The audit was ordered by the government to evaluate transport safety following deadly air accidents in recent months.

First, an Adam Air jet carrying 102 people disappeared in January, and on March 7 a Garuda plane overshot a runway and burst into flames, killing 21 people.

Radjasa, who has faced calls to resign from parliamentarians after the string of disasters, outlined a roadmap to improve the nation's shoddy transport system by 2009.

"Many of our ships are more than 20, or perhaps 30 years old, our aircraft are mostly over 20 years old and our railway track dates back to colonial era," the white-haired Radjasa said.

Patchy Radar Cover

He said Indonesia's patchy radar cover should be extended to cover 100 percent of national airspace by 2009, while there would be more security X-ray machines for security purposes.

He said that the budget for transport had been increased by 15 percent this year to around 16 trillion rupiah (US$1.8 billion) for the transport sector, but would seek other sources of funding including the private sector for such a huge task.

The U.S embassy message said the recent accidents "raise questions about the safety practices of Indonesian air carriers and their oversight by the Indonesian Directorate General of Civil Aviation".

Air travel in Indonesia, a sprawling nation of more than 17,000 islands, has grown substantially since the liberalization of the sector in 1999 which triggered price wars among airlines.

The rapid growth caused concern over whether safety has been compromised and aviation infrastructure and personnel can cope with the huge increase.

In a separate written response to questions, Radjasa denied that budget airlines had operated by skimping on safety.

"It is not true that the budget airlines run by cutting safety related cost," he told Reuters by fax.

Indonesia is also grappling with problems in other modes of transportation.

Two serious ferry disasters in recent months killed hundreds of people, while rail accidents on an aging system built during the Dutch colonial era occur frequently.

(US$1=9085 Rupiah)