Incidents of unruly behavior from airplane passengers has risen to an unprecedented level this year, union leader Sara Nelson told CNBC on Friday, the start of the Memorial Day holiday weekend. “This is an environment that we just haven’t seen before, and we can’t wait for it to be over,” the president of the Association of Flight Attendants-CWA said on “Squawk Box.” The behavior has become “complete nuts,” added Nelson, whose union represents around 50,000 cabin crew members across more than a dozen carriers. “It’s a constant combative attitude. ... It’s got to stop.”