On this day in history - April 20

What Happened On This Day – April 20

• 2010 The Deepwater Horizon oil rig explodes

  The explosion of the British Petroleum (BP) platform operated by Transocean killed 11 workers and led to the largest accidental marine oil spill in history.

• 1999 15 die in the Columbine High School massacre

  A further 24 victims were injured when two teenagers opened fire on students and teachers in the high school south of Denver.

• 1978 Soviet air defense shoots down Korean Air Lines Flight 902

  The Boeing 707's crew had miscalculated their route, taking them into Soviet airspace at the height of the Cold War. The jet made an emergency landing on a frozen lake. Two passengers were killed in the incident.

• 1951 A human organ is surgically replaced for the first time

  Romanian surgeon Dan Gavriliu used a section of the stomach to bypass the esophagus.

• 1902 Pierre and Marie Curie discover the radioactive element radium

  In 1903, the French couple received the Nobel Prize in Physics for their pioneering research.