[gmueckl]

Yes, they exist in Europe, they ban be dirt cheap, executed by companies run by penny pinchers and mostly superfluous. Going by train is in many cases faster because it gets you from city center toncity center without any airport overhead. But it also costs a multiple of a plane ticket, which should not be the case.

[ChuckNorris89]

Yes but the cases when taking such short flights instead of trains make sense is when you commute form a small city airport to an international hub for a layover to an international flight and that saves you lots of time as you've already been through security once and you're already inside the airport fairly close to your departure gate so you can arrive pretty close time wise to your next flight as opposed to having to commute from the train station to the airport and be there ~2 hours before the flight to clear security and all.

Nobody takes the plane for 30 min to get from city center to city center, we do it because we have to catch another flight from that city's airport and it's quicker by plane.

[Marsymars]

To note - very small city airports don't have security to pass through. Of course, at those population densities, trains don't make sense anyway.