Masks will remain compulsory on US flights until mid-January as cases of the COVID-19 Delta variant continue to surge in America. The mask mandate, which also covers trains and buses, was due to expire on September 13 but a Transportation Security Administration official confirmed the plans to extend it. The official said the extension was intended to minimize the risk of COVID transmission on public transport. Airlines were briefed about the plan on Tuesday, according to US media. READ: Qantas to demand all staff be vaccinated. Association of Flight Attendants-CWA president Sara Nelson, whose union represents about 50,000 flight attendants at 17 airlines, welcomed the extension. Nelson said everyone looked forward to the day masks were not needed “but we’re not there yet”. "Masks are the most effective tool to stop the spread of COVID-19. While vaccination has been key to the increased air travel demand, the lagging vaccination rates and rise of the Delta variant has caused cases to skyrocket again - threatening lives, continued virus mutation, and recovery from this pandemic,” she said. Most people comply with the mask rule but it has been a source of tension on aircraft and about three-quarters of unruly passenger reports this year have stemmed from mask issues. Fines for not wearing a mask range from $US250 for the first offense to $US1500 for repeat offenders but this can morph into a much bigger fine if an incident involves disruptive behavior. According to the Centers for Disease Control,  face masks should cover the nose and mouth and fit snugly against the sides without gaps. They can be either manufactured or homemade and should be a solid piece of material without slits, exhalation valves, or punctures. While medical masks and N-95 respirators fulfill CDC and TSA’s requirements, face shields and/or goggles are not an acceptable substitute but can be used in addition to an acceptable mask. Meanwhile, Australia’s ABC reported Wednesday that a drunk man who vaped and grabbed a fellow passenger on a Jetstar flight to Hobart was fined $4000 for offensive behavior. The passenger pleaded guilty to the offenses, which included telling the cabin crew to f*ck off when asked to stop vaping, grabbing a fellow passenger around the chest and swearing at police. Magistrate Michael Daly described the decision to vape on an aircraft as “arrogant and outrageous”.