Cantor Fitzgerald has boosted its damages claim in the Sept. 11 terror attacks by more than $1 billion to cover lost profits after two-thirds of its work force perished in the World Trade Center collapse.

The financial services firm — which initially sought only $102.5 million — demanded the eye-popping amount “on the eve of mediation” last year, according to a new Manhattan federal court filing.

Defendant American Airlines — whose Flight 11 crashed into the north tower — will seek to have the “dramatic increase” dismissed on grounds that it’s a “disguised wrongful death claim” with no basis in law, the court papers say.

A Cantor spokesman declined to comment.

Cantor’s claim was revealed in an agreement to settle $6 billion worth of property-damage suits filed by 80 businesses, including the former Windows on the World restaurant, World Trade Center Farmers Market and numerous insurance companies.