Twenty-one years after the September 11 terror attacks, Australia's leaders have remembered those who were killed.
Ten Australians were among the almost 3000 people who died when al-Qaeda militants hijacked four planes on September 11, 2001.
The hijackers flew two planes into the twin towers at the World Trade Centre in New York and one into the Pentagon just outside of Washington.
The fourth plane crashed into a field in rural Pennsylvania.
Those who died and the thousands of others who were injured would never be forgotten, Prime Minister Anthony Albanese said.
"The images from that dark day do not fade. But nor do our memories of those who were lost, and those left with loss," he said in a tweet on Sunday night.
"We remember the compassion and courage that day, and how it proved greater than any enemy."
Federal Opposition Leader Peter Dutton also paid his respects.
"We remember those who lost their lives and all those still living with the loss of loved ones," Mr Dutton said in a statement on Sunday.
"In so doing, we reflect on our fortitude as free people and the enduring strength of our values.
"We can overcome unimaginable tragedy and rise to meet the most trying of challenges as long as we continue to confidently and courageously carry the flame of liberty and justice."
Americans will on Sunday remember the deadliest terror attack on US soil through candlelight vigils, interfaith services, and other commemorations.
