French MPs approved a measure this week that will rule out domestic flights between destinations that can be reached by train in under two and a half hours. The compromise made in defining this distance has left the blanket ban at an uncomfortable middle ground: it is too small to have a material impact on the country’s CO2 emissions; but it is too large to leave room for bottom-up innovation in the country’s emission-free aviation. The ban comes as part of a bill to cut France’s greenhouse emissions by 40% between 1990 and 2030, which has been widely criticized for lack of ambition – the EU, by contrast, is seeking a 55% reduction. Along with the ban on short domestic…