A man has been questioned by police at LaGuardia airport in New York after smuggling a monkey onto a flight from Florida by hiding it under his hat.

Passengers spotted the animal when it climbed out and perched on the man's ponytail, Spirit Airlines spokeswoman Alison Russell told reporters.

The man's journey originated in Lima, Peru. Ms Russell said it was not known how the man avoided detection there, and during a several-hour stopover in Fort Lauderdale, Florida.

When passengers noticed the fist-sized primate on the flight, they asked the man "if he knew he had a monkey on him", Ms Russell said.