A tourist takes a photo as the Acropolis’ Propylaea are seen in the background, in Athens, Greece, on June 28, 2024. Elias Marcou | Reuters Flights between the U.S. and Europe have not been this cheap in three years, when many countries were just lifting Covid-19 era rules. Fares are low even for the traditionally slow late-fall and winter months outside of major holidays. “It is brutal to fill seats