All 21 passengers injured in a Delta Air Lines crash Monday have been released from the hospital, according to Delta.Video above: Passenger describes Toronto plane crash"The Delta and Endeavor families are grateful that all those injured Monday have been released from the hospital, and we extend our thanks to everyone who provided care to them over the past few days," said Delta CEO Ed Bastian. "We will continue to connect one-on-one with customers, employees and loved ones as we move forward to make sure their needs are met with care."The passenger jet made a hard landing before it lost a wing, burst into flames and flipped onto its roof at Toronto's airport. Although 21 people were injured, all 80 people on board the flight from Minneapolis survived the crash.Here are some things to know about the crash:What caused the airplane to flip?Investigators and airport officials have been careful to avoid talking about what went wrong when the plane touched down.Communications between the tower at Toronto's Pearson International Airport and the pilot were normal on approach and airport officials said Monday was a clear day with normal operations before the crash.Video below: New video shows Toronto crash landingWhat are investigators focusing on?Aviation experts said investigators will consider whether the pilot바카라 게임 웹사이트�s actions, potential landing gear problems or weather conditions caused the hard landing.Were strong winds a factor in the crash?Toronto Pearson Fire Chief Todd Aitken said the runway was dry and there was no crosswind conditions. Audio recordings indicate the control tower warned the pilots of a possible air flow 바카라 게임 웹사이트�bump바카라 게임 웹사이트� on the approach. Winds were gusting up to 40 mph.But airplanes and pilots should be equipped to handle those kinds of winds while landing, said John Cox, CEO of aviation safety consulting firm Safety Operating Systems in Florida.Were the passengers badly injured?All of the 21 people who were transported for treatment been released from hospitals. Some of those injured were exposed to leaking fuel, according to airport fire officials.What happened inside the plane?One passenger told CBC 온라인 바카라 게임 that he found himself upside down and still strapped in his seat after a forceful landing.Peter Carlson said he crashed onto the ceiling when he took off his seat belt and smelled gas. He and another man helped a mother and her young son out of the plane before getting out.Most of the passengers were able to begin evacuating on their own, fire officials who responded to the crash said.Who is investigating?The U.S. Federal Aviation Administration said the Transportation Safety Board of Canada will lead the investigation. The National Transportation Safety Board in the U.S. was sending a team to assist.Is it safe to fly?The fourth major aviation accident in North America in less than a month has many people concerned about the safety of flying. Fatal crashes remain rare and the track record of U.S. airlines is remarkably safe.But there have been deadly crashes recently around the world and U.S. officials have been raising concerns about an overtaxed and understaffed air traffic control system for years.