BERLIN (Reuters) – Germany’s longest-ever rail strike is offering a boost to transport companies, who have reported a surge in bookings as people look for alternative travel options on the roads and in the skies. “Demand has more than doubled,” said a spokesperson for FlixBus, which operates intercity bus services across Europe. The increase in bookings has been stronger than during previous strikes at state rail operator Deutsche Bahn, the spokesperson added. Train drivers are set to strike from Wednesday morning until the following Monday evening, the GDL union’s longest walkout yet in a mon…