A millionaire activist who believes the September 11 terrorist attacks in 2001 were and "inside job" is offering a $130,000 reward to anyone who can prove him wrong.
Jimmy Walter has spent more than $3.9 million promoting the conspiracy theory and is offering the reward to any engineering student who can prove the World Trade Centre buildings crashed the way the Government says they did.
"Of course, we expect no winners," Mr Walter, 57, heir to an $14.3 million fortune from his father's home-building business.
He accuses figures in government, the military and business of involvement in the September 11 attacks.
Mr Walter says a panel of expert engineers will judge submissions from the students.
Next month he also launches a nationwide contest seeking alternative theories from college and high school students about why New York's World Trade Centre collapsed.
The contest offers $13,000 to the best alternative theory, with 100 runner-up awards of $1,300. Winners will be chosen next June.
Various official investigations give no credence to Mr Walter's theory.
A September 11 commission spokesman said its policy was not to comment on criticism of the official report into the attacks.
Mr Walter insists there had to be explosives planted in the twin towers to cause them to fall as they did and also rejects the official explanation for the damage done at the Pentagon.
"We have all the proof," said Mr Walter, citing videotapes and testimony from witnesses.
"It wasn't 19 screw-ups from Saudi Arabia who couldn't pass flight school who defeated the United States with a set of box cutters," he said.
He dismissed the official September 11 commission report, saying: "I don't trust any of these facts."