"Hey, moron - things that use a lot of energy are expensive to operate. Physics dictates the economics. When you have to slow or stop a train then accelerate again it takes a LOT of energy. That energy has to come from somewhere, and since you can't power a train with solar that means BUYING the energy"
stopping and starting a train still doesn't take as much energy as an airplane taking off. All you really have to do to slow down a train is to decrease the power output. Also, trains can be powered with solar power.
Economics-wise, trains are a lot more efficient than planes. A plane has to be completely full to make a profit, while a train has to be just over 60% full. A pilot's salary is near double that of a train conductor's, and most commercial airplanes have 2 pilots. Airplanes need a specific explosive fuel to be usable, while trains can be powered with a reasonable electricity supply.