Mark Zuckerberg’s sister isn’t the first to complain about sexual misconduct on jetliners — a problem a prominent flight attendants’ union called a “silent epidemic” that airlines have failed to solve. Randi Zuckerberg, a media executive, said this week that a male passenger on an Alaska Air flight made repeated harassing comments to her and airline employees did nothing about it. In a letter to the carrier posted on social media, the sister of the Facebook founder said the crew members continued to serve the abusive customer alcoholic drinks and told her not to “take it personally. Zuckerberg’s description of the incident on a trip from Los Angeles to Mazatlan, Mexico, drew widespread media attention and Alaska Airlines temporarily revoked the passenger’s travel privileges, pending an investigation. Still, airlines must take stronger action to crack down on in-flight sexual harassment and assault, said Sara Nelson, international president of the Association of Flight Attendants-CWA.