Two college professors who submitted a design for a memorial to those who died aboard United Flight 93 on Sept. 11, 2001, say changes made to the winning submission include elements of their entry, and they want credit for them.

But officials with the Flight 93 memorial, to be built on the site of the crash near Shanksville, said any similarities are just coincidence. Many of the more than 1,000 designs that were submitted contained similar themes, they said.

Lisa Austin and Madis Pihlak claim the winning design includes about 10 ideas included in their submission, titled Sacrifice. They include a break in a grove of trees to mark the flight path, a sound element built 93 feet high, the planting of blue coneflowers at the entrance and a curving wetlands path.

The pair said the winning design, created by Los Angeles-based Paul Murdoch Architects, did not originally include anything from their design. However, the Murdoch plan was redesigned last fall to change a crescent shape that some people deemed offensive, and the resulting design included elements of Sacrifice, Austin and Pihlak claim.

John Reynolds, chairman of the Flight 93 Advisory Commission, said in a statement that the redesign was based on feedback from the competition juries and many others involved in the project.

"We feel that the Sacrifice design is dramatically different from the Murdoch design in symbolic intent, physical form, quality, and means of expression," Reynolds said.

Murdoch did not return a call for comment Friday.

Austin and Pihlak contacted the National Park Service with their concerns last year. In April, a letter from the pair laying our their claims was published in Landscape Architecture magazine.

Patrick White, vice president of the Families of Flight 93 whose cousin was killed, said Austin and Pihlak's claims were investigated at the time. White said he had seen all of the contest entries and dozens had similarities because of the shape of the land, the soil type and other factors.

"Looking at it objectively, I believe that the claims have been investigated, thoroughly analyzed and the conclusion reached that they are without merit," he said.

Austin, an art professor at Edinboro University, said she and Pihlak, a professor at Penn State University's School of Architecture and Landscape Architecture, do not believe anyone stole the material from their design.

"The point of fact is that ours was published and ours was a copyrighted design ... and these are ideas that we proposed. And now, these are ideas that are going to be built," Austin said.

Flight 93 was flying to San Francisco from Newark, N.J., on Sept. 11, 2001, when it was hijacked and crashed in a field near Shanksville, about 65 miles southeast of Pittsburgh.

The original design was selected by a jury that included design professionals, family and community members. It was narrowed down from a pool of 1,011 submissions.

Austin said they have chosen not to pursue legal action because they don't want to delay the building of a memorial.

"We know that the families are waiting for a place to go to mourn their dead," she said. "We don't want to impede that process."