 U.S. airlines had made no major changes as of the beginning of June 2009 , but continued standing practices which include looking for passengers with symptoms of flu , measles or other infections , and relying on in @-@ flight air filters to ensure that aircraft were sanitised . Masks were not generally provided by airlines and the CDC did not recommend that airline crews wear them . Some non @-@ U.S. airlines , mostly Asian , including Singapore Airlines , China Eastern Airlines , China Southern Airlines , Cathay Pacific and Aeromexico , took measures such as stepping up cabin cleaning , installing state @-@ of @-@ the @-@ art air filters and allowing in @-@ flight staff to wear face masks . 
