NATO's Secretary General Mark Rutte on Thursday backed U.S. President Donald Trump's comments this week that NATO member countries should shoot down Russian drones and airplanes if they enter their airspace, if such a move was necessary. "If so necessary. So I totally agree here with President Trump: if so necessary," Rutte said in an interview on Fox News' "Fox & Friends" program, adding that NATO militaries are trained to assess such threats and determine whether they can escort Russian planes out of allied territory or take further action.