A Delta Airlines regional jet flipped upside down upon landing at Canada's Toronto Pearson Airport yesterday amid windy weather following a snowstorm, injuring 18 of the 80 people on board, officials said. Three people on flight DL4819 from Minneapolis-St. Paul International Airport suffered critical injuries, among them a child, a Canadian air ambulance official said, with 15 others also immediately taken to hospitals. Some of the injured have since been released, Delta said late last night. The US carrier said a CRJ900 aircraft operated by its Endeavor Air subsidiary was involved in a single-aircraft accident with 76 passengers and four…