Fourteen people were killed, and dozens injured.
Eyewitnesses, aware the United States was in the midst of World War II, feared the worst.
"Thought we'd been bombed," Doris Pope, Boynton Beach, Fla. told the The Palm Beach Post in 1999. "I worked for the Office of Office of Price Administration in the Empire State Building. That day, as we were getting ready to take our coffee break, we heard this terrible noise, and the building started to shake.
As we looked out our third-floor window, we saw debris fall on to the street. We immediately thought New York was being bombed.
"We were then told that an airplane hit the building," she continued.
Plane Cleared to Land in Newark
On that day in 1945, an Army Air Corps B-25 bomber headed from Bedford, Mass., to Newark, N.J., was lumbering low over Manhattan in extremely thick fog, according to reports.
Lt. Col. William F. Smith Jr., the pilot of the B-25, was told to land at Municipal Airport in Queens (now known as LaGuardia). But he insisted for clearance at Newark, according to a New York Times report.
Reports say that just as Smith was cleared to land, he was already headed toward disaster. Government regulations said that aircraft should fly at least 2,000 feet over Manhattan. The plane struck the building 913 feet above the ground, at 34th Street in midtown. The plane's nose had crashed into the building's north side.
"It was rainy, overcast," Louis Triandafilou, an Army Air Forces photographic lab chief stationed at Newark Airport who took aerial photographs of weather conditions told the Clearwater Times in 1991. "You couldn't see the peak of the Empire State Building, and part of the Statue of Liberty's torch was obscured by fog."
When the plane crashed, one of its engines whizzed from the north wall, and through the south wall, ultimately landing on the roof of a nearby building. Debris from the building and plane also severed through elevator cables, and sent two cars and passengers into freefall.
Smith was killed, along with the other two crewmembers, in addition to another 11 people working at their desks, and over two dozen more were injured. The workers were on the staff of the National Catholic Welfare Service, now known as Catholic Relief Services, who still keep their offices on the 79th floor.
About $1 million in damage was reportedly done to the building. Because it was Saturday, the offices were not fully staffed, perhaps preventing more damage and injuries, reports say.
Eyewitnesses Remember Panic
Eyewitnesses who are still alive and were there for the incident remember midtown Manhattan being in a state of panic.
"I heard a horrendous noise," eyewitness Helen J. Hurwitt, from Greenacres, Fla., told the Post. "My husband and I were in a building directly opposite the Empire State Building.
Large plate-glass windows looked out onto 34th Street. The floor we were on was pretty high. At some point, we heard a horrendous noise and rushed to the windows.
We were horrified to see a B-25 half in and half out of the Empire State Building."
Reports say that it took three months to repair the 78th and 79th floors, both of which were damaged. Crews had to repair bent girders, seal the walls, and restore the two floors of offices.
Today, the building remains structurally sound, say reports.