United Airlines concerned about fourth plane

One of the planes that crashed into the Trade Center was American Airlines

American Airlines issued a statement saying it had "lost" two aircraft – Flight 11, with 92 people aboard, and Flight 77 from Washington to Los Angeles, carrying 64 people.

In Pennsylvania, United Airlines Flight 93, a Boeing 757 en route from Newark, N.J., to San Francisco, crashed about 80 miles southeast of Pittsburgh.