The most lucrative air travel markets in the United States are undeniably transcontinental flights, especially those that serve major economic hubs heavily saturated with business travelers. When flying from major East Coast cities like New York, Boston, and Philadelphia, to West Coast cities like San Francisco, Los Angeles, and Seattle, airlines will often operate services during the day. In the reverse direction, these flights will often follow a red-eye schedule, something which allows carriers to charge business travelers for lie-flat seats, as they will often pay for the convenience of a flatbed seat.