Kadir, an ex-parliamentarian of the South American republic of Guyana, was charged with trying to arrange financing for the planned attack.
The pair were arrested in 2007 after an informant infiltrated the plot.
The government's case relied heavily on tapes - secretly recorded by the
informant - of Defreitas bragging about his knowledge of the airport and its vulnerabilities.
On tape, Defreitas, a naturalised US citizen from Guyana, talked about punishing the US with an attack that would "dwarf 9/11".
He told the informant his US citizenship gave him cover.
"They don't expect nobody in this country to do something like this," he said.
"They have their eyes on foreigners, not me."
The defence had argued that the men were led astray by the informant. Kadir
testified that he was against attacking innocent victims.