Navigating a country of 17,500 islands scattered across three time zones has never been easy. Now it is downright scary for many air travelers.

Twice this year, Indonesian airliners have crashed, leaving more than 120 people dead. A Transportation Ministry audit released late last week found that none of 20 major Indonesian passenger and cargo airlines fully meets national safety regulations.

The news, coming in the wake of a series of ferry disasters, shook Indonesians already nervous about taking a trip. "I think consumers have some kind of mental trauma that makes them think twice before flying," said Tulus Abadi, a leader of the Indonesian Consumers Organization.

And Australian foreign affairs officials issued an advisory warning Australians to take the report into account before making travel plans in Indonesia.

Like most Asian countries, Indonesia is in the midst of a transportation revolution as competition drives down prices to make air travel affordable for people who once had to rely on boats, buses and cars. But to keep fares low, airlines fighting for customers have cut corners, the government audit shows.

All of the airlines meet minimum safety requirements, but none is good enough to qualify as an excellent carrier, Budhi Mulyawan Suyitno, Indonesia's new director general for air transportation, said in an interview.

Seven airlines ranked in the lowest of three categories, and 13 placed in the middle. He said that if those in the middle "made just a little effort and worked harder in these coming months, they can be upgraded to the top category."

The most serious problems included insufficient pilot training and aircraft flying without reserve fuel, Suyitno said.

Other shortcomings detected by the audit included relatively minor infractions, such as using flight data and cockpit noise recorders that were out of date and would make accident investigations more difficult.

Suyitno declined to name the worst offenders, insisting that would "be biased."

The government has given airlines three months to improve or face penalties, such as having aircraft grounded or licenses revoked.

"In this airline business, the potential for failure is big," Suyitno said. "That is why we need strict regulation. We don't allow even a tiny space for error. This error can happen because the human factor is dominant."

A state-owned Garuda Indonesia Airlines Boeing 737-400 overshot the runway at Jogyakarta airport and burst into flames March 7. The crash killed 20 passengers and one crew member. Another 119 people survived, including the pilot and co-pilot.

The pilot said he felt a powerful downdraft during landing. Survivors told of the aircraft bouncing hard off the runway at least twice.

Investigators are probing claims that the plane was traveling too fast on its approach. Some experts have speculated that wing flaps might have malfunctioned.

Two months before the Garuda crash, a budget-fare Adam Air jet disappeared off the west coast of Indonesia's Sulawesi island, killing all 102 people aboard.

Indonesian airline safety is suffering because some of the new airlines are run by people with lots of money but too little experience, said consumer advocate Abadi.

Corruption and nepotism in issuing expensive operating licenses only raises the risks, he charged.

"But the most important factor is lack of supervision from the government," he added. "The government is very kind, freely giving operating licenses to new airlines, which creates an oversupply. But then the government fails to supervise, which makes conditions worse." Abadi called on Indonesian authorities to shut down airlines with the worst safety records instead of protecting cheap air travel at any cost.

"Do not gamble on people's lives only to defend something that is short-term," he said.