Flight 93 was headed towards Three Mile Island. On that day, the NRC placed all of the nation's nuclear power plants into the highest level of security. United Flight 93 crashed into a field about 135 miles west (217 km) of Three Mile Island in Stonycreek Township, just outside Shanksville, Pennsylvania, with its actual target believed to be intended for Washington, D.C. On November 21, 2009, a release of radioactivity occurred inside the containment building of TMI-1 while workers were cutting pipes. Exelon Corporation stated to the public that "A monitor at the temporary opening cut into the containment building wall to allow the new steam generators to be moved inside showed a slight increase in a reading and then returned to normal. Approximately 20 employees were treated for mild radiation exposure." , it was believed that no radiation escaped the containment building and the public was not in any danger. The inside airborne contamination was caused by a change in air pressure inside the containment building that dislodged small irradiated particles in the reactor piping system. Some of the small particles became airborne inside the building and were detected by an array of monitors in place to detect such material. The air pressure change occurred when inside building ventilation fans were started to support outage activities. The site modified the ventilation system to prevent future air pressure changes. Work continued on the project the following day. On January 24, 2010, TMI-1 was brought back online. Material handling accident On September 10, 2021, a contractor from Alabama was fatally injured while unloading equipment from a truck. Fire and emergency medical personnel from Londonderry Township were dispatched and declared the contractor dead on arrival. The Nuclear Regulatory Commission said the injury was work-related, and the contractor was outside the radiological controlled area. Three Mile Island Unit 2 The Three Mile Island Unit 2 was also a pressurized water reactor constructed by B&W, similar to Unit 1. The only difference was that TMI-2 was slightly larger with a net generating capacity of 906 MWe, compared to TMI-1, which delivers 819 MWe. Unit 2 received its operating license on February 8, 1978, and began commercial operation on December 30, 1978. TMI Unit 2 has been permanently shut off after the Three Mile Island accident in 1979. Accident On March 28, 1979, a cooling system malfunction caused a partial meltdown of the reactor core.