Flight 93 crashed in Pennsylvania and exploded in midair over Pennsylvania’s Pennsylania countryside, killing all 259 people on board.
The wreckage from the jetliner, which took off from Newark, N.J., crashed near Pittsburgh.
The National Transportation Safety Board said that at least two airliners, a United Airlines flight from Minneapolis and an Air France flight from Paris, were flying at the time of the crash.
NTSB investigators believe the crash was caused by a mechanical failure that caused the plane to fly over the area of Pennsyliania.
The agency says it is working to determine how the plane was flown over the mountainous terrain.
One of the planes that crashed was United Airlines Flight 77.
The crash happened at about 8:30 p.m.
EDT on Wednesday, and investigators have said they don’t know the cause.
The plane was heading toward the Philadelphia area when it went down in Pennsylvania.
There were no survivors, the NTSB said.
It was the second plane to crash in Pennsylvania in as many days.
In a statement, Pennsylvania Gov.
Tom Corbett said that the incident in Pennsylia is being investigated by the National Transportation Security Board and that he is confident that the investigation will determine whether the incident was caused or contributed to by a pilot error.
Authorities said the jet was carrying 175 passengers and four crew members.
The Pennsylvania state police are investigating the incident.