Two men were charged with terrorism offenses in Australia on Thursday in connection with an alleged plot to bring down an airplane, police said.

The men, ages 49 and 32, were each charged with two counts of planning a terrorist act, Australian Federal Police said in a statement. They were among four men arrested during a series of raids in Sydney on Saturday in connection with what authorities described as a credible threat to bring down a plane.

A third man remains in custody but has not yet been charged, while the fourth man was released without charge on Tuesday.

Officials have provided few details of the alleged plot, including the precise nature of the threat or any airlines involved. On Tuesday, the United Arab Emirates’ national airline, Etihad Airways, said it was working with Australian police in the investigation, suggesting one of its planes may have been targeted. Etihad refused to confirm, however, if it had been a target.

Earlier Thursday, Prime Minister Malcolm Turnbull said there was no longer any threat to Australia’s aviation industry from the alleged plot.

Turnbull said the country’s intelligence agency is restoring the aviation threat level to what it was before the men were arrested.

“The threat to aviation from the plot that was uncovered to bring down a plane has been disrupted and contained,” Turnbull told reporters in Perth.

Security was increased at all major Australian international and domestic terminals following the arrests, leading to massive lines and delays for travelers. On Thursday, Turnbull said while enhanced security measures will continue, they will be modified to reduce delays. He declined to offer any details on what changes will be made.

Passengers this week were urged to arrive at airports an hour earlier than they normally would, but Turnbull said he expected the suggested arrival times to return to normal within the next day.

(AP)