Queuing to board a flight at Avalon Airport on Friday, Geelong resident Natalie Bowdery was feeling a tad apprehensive. "It's pretty scary and alarming and I think a lot of us are thinking how could that possibly have happened, but I'm still trying to be positive about the trip today," she said. A day earlier, a teenager allegedly armed with a shotgun entered a Jetstar plane en route to Sydney. The incident has sparked questions around whether security measures at regional airports are stringent enough. What happened on the Jetstar plane at Avalon Airport? On Thursday afternoon, a 17-year-old boy allegedly boarded a flight to Sydney armed with a loaded shotgun, telling passengers that he had bombs in his bag. He was dressed in a high-vis jacket when he entered the plane and was questioned by a Jetstar cabin manager. A group of passengers and the pilot tackled the boy to the ground, detaining him while waiting for police to arrive. He faced the Children's Court on Friday charged with offences including unlawfully taking control of an aircraft, endangering the safety of an aircraft, carrying out a bomb hoax and possessing a firearm. According to charge sheets released by the court, the teenager also planted a fake homemade explosive and threatened passengers and crew. How did the 17-year-old manage to board the plane? Police say the teenager entered the airport through a hole in the security fence, and later found two bags and a vehicle belonging to the boy. Avalon Airport chief executive Ari Suss said the airport had since undertaken an enhanced level of security to reassure the public of their safety. "We undertake our own reviews with regards to security issues at Avalon," he said. "We are confident that Avalon is working to address all these issues in our discussions and actions with the key agencies." Aviation law and safety expert Robert Bartsch said the breach was not acceptable and any passenger boarding a commercial jet aircraft in Australia was entitled to the same level of security. "Security systems have got to accommodate all possible scenarios and it's not inconceivable that someone with some wire cutters or whatever can cut through a fence, so it makes a mockery of having sophisticated scanning and security systems," he said. A spokesperson for the Department of Home Affairs said the agency was "onsite conducting initial assessments and will continue to work closely with Avalon Airport and Jetstar". What security is in place at Avalon Airport? Victoria Police is not stationed at Avalon Airport, with the airport instead patrolled by a few private security groups. Airports and their security requirements are determined by categories called "tiers", with top tiers being major airports and bottom tiers being smaller, remote aerodromes. Capital city airports like Tullamarine are considered to be tier one, while Avalon Airport, as a non-capital international gateway airport, is designated as tier two. Tier one airports are policed by the Australian Federal Police (AFP), while tier two airports do not require a permanent police presence. Federal government tenders show the airport received hundreds of thousands of dollars in security upgrades, including more than $700,000 for security surveillance and detection between 2018 and 2019. Geoffrey Askew, a principal at Askew and Associates, who was previously the global head of security for the Qantas group, said tier one and two airports had different fencing requirements and therefore could not be compared. "It's not a military camp. It's not a place of war … it's an international airport. But there is no guarantee that a fence would keep people out," he said. "The quality of the fence is certainly important but there needs to be some supporting technology and a lot of that is dependent on the people who work airside. Mr Askew said many of the grants given to regional airports were for screening technologies within terminals but he said the focus needed to be redirected to more monitoring around perimeters using modern technologies. The federal government offered nearly $50 million in grants to some regional airports to improve their security screening measures through its Regional Airport Security Screening Fund. The Australian Airports Association (AAA) said airports were safe environments, processing up to 120 million customer movements in and out of city and regional airports. "Fence lines at all of our airports … are regularly monitored," AAA chief executive Michael Westaway said. "The event shouldn't have happened and we need to get to the bottom of why it occurred." Mr Westaway said whether or not an airport was patrolled by police was irrelevant, and that the focus should be on delivering security services efficiently and compliantly. What have airline workers had to say? Transport Workers Union (TWU) national secretary Michael Kaine said the security breach at Avalon Airport was "outrageous" and "unacceptable". "Someone was able to walk through the airport and onto a plane, armed. Just saying those words is an absolute shock," he told reporters on Friday. He said an incident like this sent shock waves through the industry. "The ripple effect means that we now have an aviation workforce that is on tenterhooks," Mr Kaine said. He said the aviation industry was in crisis and cited a recent TWU survey of more than 2,000 aviation workers that found that more than half feel unsafe in their jobs and had had to deal with threatening situations. "Urgent action has to be taken to address this crisis … because at some point this type of incident is going to end up in catastrophe," Mr Kaine said. "Workers and passengers should not have to board an airline to get to their destination feeling like somewhere in their person they have to have some Rambo element ready to fight, literally, for their lives." What is security like at other regional airports? Mr Askew said there needed to be an increase in security at regional airports as the risk was not solely present in airports with international flights or larger aircraft. His concern was the lack of screening at some smaller airports and the impact on passenger safety. "You're getting on an aircraft of 60 or 50 people and there's no screening — I'm not sure that passes the pub test these days," he said. But Mr Askew said the cost of improving security at airports would fall onto airlines and their passengers without more government funding. He said some airline operators could also choose to withdraw from airports if burdened by extra costs if the upgrades were not enforced by regulations. "The government will review [regulations] on a regular basis and determine, depending on the threat level nationally and also for the aviation industry," Mr Askew said. "At the moment, there are smaller regional airports where passenger screening is not required by regulation." The AFP said it had met with Victoria Police to discuss the incident. "The AFP's Counter Terrorism and Special Investigations Command is working alongside Victoria Police after a security incident at Avalon Airport," the AFP said.