OTTAWA - Thou­sands ordered to flee wild­fires advancing on one of the largest cities in Canada’s far north crammed into a lo­cal airport on Thursday to board emergency evacuation flights, as convoys snaked south to safety on the only open highway. The order late Wednesday to evacuate Yel­lowknife in the Northwest Territories marked the latest chapter of a terrible sum­mer for wildfires in Canada, with tens of thousands of people forced to leave their homes and vast swathes of land scorched. Tiffany Champagne was one of many awaiting flights at the airport in Yellowknife. “I have asth­ma and the wildfire smoke was making it increasingly difficult to do anything,” Champagne, wearing a face mask, told the CBC. “I’m just kind of mentally checked out at this point.”