A number of European countries have been asking their citizens to avoid short-haul flights between their countries.

It’s not just an environmental concern, but it’s one of efficiency.

A small 737 or Airbus flying between London and Paris, or between Amsterdam and Vienna, takes up the same gate space as a jumbo jet and needs the same separation in the skies.

Now, there’s an economic case to avoid short-haul flights.

For example, a coach ticket from Vienna to Paris can be as high as $350. However, a sleeper train starts at only $105 for private sleepers, breakfast delivery, private toilets, and showers.

A coach ticket from Zurich, Switzerland to Zagreb, Croatia hovers around $500. But the cost for a private sleeper is about $150.

Finally, the coach flight from Milan to Palermo costs around $200. But by train, it’s only about $68 and includes a ferry ride across the Strait of Messina.