THE United States was so concerned about the state of Australia's air safety system in 2009 that it considered freezing flights from Australia to the US, a downgrade that normally only affects countries from the developing world.

The revelation, in a US State Department cable released this week by WikiLeaks, discussed a recent safety inspection by the US's Federal Aviation Authority, which audits countries whose carriers fly to the United States to ensure they meet appropriate safety standards.

In the cable, from December 2009, it is revealed the FAA told Australia's Civil Aviation Safety Authority that Australia could face a downgrade to ''Category 2'' due to a shortage of properly trained safety inspectors and too much delegation of CASA's regulatory function to carriers.

A Category 2 rating suggests the FAA believed the country's safety regime does not meet international standards. It is a category mainly used for countries in the developing world.

''A downgrade to Category 2 would be the worst-case scenario, which would entail measures such as freezing Australia-US flight operations to current levels and terminating code-sharing arrangements, such as the one between Qantas and American Airlines,'' the cable stated.