Total money raised for the project now totals $30 million, King Laughlin, vice president for the Flight 93 National Memorial said.
The Pittsburgh Tribune-Review said the final $5 million left to be raised will finance construction of a learning center and the design and construction of a "Tower of Voices" that will contain 40 wind chimes at the memorial site.
The memorial honors the 40 passengers and crew aboard the United Flight 93 who died on Sept. 11, 2001, when the passengers thwarted terrorists' plans to crash the jet into the Capitol and instead, crashed the plane down in a field near Shanksville, Pa.
Construction of the visitors' center is expected to begin in May and will take about 20 months, the Pittsburgh Tribune-Review said.
The visitors' center will have permanent exhibits and the learning center will offer changing programs, photography exhibit and speakers.
The Pittsburgh-Tribune Review said the memorial's first phase was dedicated on Sept. 10, 2011, and it attracted 318,000 visitors in 2012.