Authorities say more and more people are visiting the Flight 93 National Memorial in rural western Pennsylvania, and new construction is scheduled to begin next year.
The vice president of the Flight 93 National Memorial Campaign, King Laughlin, says that at the current pace more than 1,000 bus groups will visit the park this year, almost double the number in 2011.
More than 200,000 people are expected to visit this year.
United Flight 93 was traveling from Newark, N.J., to San Francisco when it was hijacked by four terrorists in 2001.
The 9/11 Commission says the terrorists likely wanted to crash the plane into the White House or the U.S. Capitol, but the jet went down in a field near Shanksville, Pa., after passengers fought back.