Canada’s federal government is considering privatizing some of the country’s airports, a proposal that could net the government as much as Cdn $16.2 billion, a proponent says in a report for the C.D. Howe Institute, an economic think tank. But the idea is fraught with knotty legal issues, already drawing pushback from some in the air transport industry and, even if the Liberal administration endorses it, could take a decade to do.