By Anna Del Savio—Reprinted with permission from the Northwest Labor Press Over the past decade, America’s largest airlines have become steadily more unionized. When the Labor Press started tracking airline unionization in 2012, the top airlines ranged from 70% to 85% union; today they’re 80% to 87% union. Delta — the largest airline by passenger miles traveled — remains the one big exception, with just 20% of its employees represented by a union.