The airline would charge for meals and baggage, O'Leary said. It would also rely on "a very high number of business or premium seats" to cover the cost of the flight, he said.
"We can make money on 99 cent fares in Europe," he said, adding, "not every seat will be 10 pounds."
However, O'Leary told a conference of hotel professionals tickets to New York or Boston would be $16.60 or 10 pounds, while the fare for a flight to Europe would be $12.50, the Telegraph reported Wednesday.
He also said the airline expects to fly from 14 major European cities to about the same number in the United States.
The flights are not expect soon, as O'Leary has said Ryanair would need "a fleet of 30, 40, 50 aircraft and not two, four or six" to get a cross-Atlantic service started.
That could take up to five years, the newspaper said.