Transportation Secretary Sean Duffy warns a 'substantial' number of Americans won't be able to travel for Thanksgiving

Secretary Duffy warns that not everyone will make their flights for Thanksgiving.Anna Moneymaker/Getty ImagesTransportation Secretary Sean Duffy says travel could slow to a trickle over Thanksgiving.Thousands have flights are being canceled as air traffic controllers go unpaid during the shutdown.The number of Americans unable to make flights home for the holiday will be "substantial," he said.If you're traveling for Thanksgiving, it might be wise to have a backup plan.Transportation Secretary S