Swissair Flight 111 was a plane that had lots of people on it and was flying from New York City to Geneva, Switzerland. However, while the plane was in the air, something went wrong and it crashed into the ocean near Nova Scotia, which is in Canada. Sadly, all 229 people on board the plane died in the crash.
What happened was that there was a problem with the electrical system on the plane, which caused smoke to go into the cockpit (where the pilots sit and fly the plane). This made it hard for the pilots to see and control the plane. They tried to land the plane at the nearest airport, but unfortunately, they didn't make it and the plane crashed into the ocean.
After the crash, people from all over the world worked together to try to understand what happened and how to prevent something like this from happening again. They learned that there were some things that could be changed to make planes safer, like making sure planes have better electrical systems and building systems that would allow pilots to control the plane even if there's smoke in the cockpit.