Menzio has been a member of Penn's faculty since 2005 after getting his Ph.D from Northwestern University. Last year, he was awarded the prestigious Carlo Alberto Medal as the best Italian economist under 40.
Menzio was headed to Syracuse to Ontario to speak at Queen's University at a macroeconomics workshop.
In a deleted Facebook post, Menzio wrote: "The lady just looked at me, looked at my writing of mysterious formulae, and concluded I was up to no good. Because of that an entire flight was delayed. . . . Trump's America is already here. It's not yet in power though."
American Airlines confirmed the woman had raised suspicions about Menzio.
A spokesman for American Airlines, said the woman initially told the crew she was sick.