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Australia's prime minister says there is no longer any threat to Australia's aviation industry from an alleged plot to bring down an airplane.

Officials say they will modify some heightened security measures that have led to long delays at airports this week.

Prime Minister Malcolm Turnbull says the country's intelligence agency is restoring the aviation threat level to what it was before four men were arrested in Sydney on Saturday in connection with what authorities dubbed a credible threat to bring down a plane.

Security was increased at all major Australian international and domestic terminals following the arrests, leading to massive lines and delays for travelers. Turnbull said Thursday while enhanced security measures will continue, they will be modified to reduce delays.