Now that “flight shame” is fashionable, Dutch airline KLM is urging short-haul travellers to take the train rather than the plane.

The reasoning behind its worthy advertising campaign is two-fold.

One reason, and the one KLM promotes, is that the carrier wants to be seen as environmentally responsible.

Another reason, not mentioned publicly, is that both KLM and its Schiphol base hope slots can be freed up for more profitable services.

As Business Traveller has reported previously, Schiphol is slot-constrained and will remain that way for some time.

But most media ignore the fact that not all short routes are the same.

For example, KLM and Schiphol hope more passengers will take the train to Paris CDG thanks to the improved high-speed Thalys service.

On the other hand, KLM gives no intention of giving up its 108-mile Amsterdam-Brussels service (a far shorter trip than Paris CDG) despite facing criticism from politicians on environmental grounds.

KLM plies Amsterdam-Brussels up to five times a day in each direction.

Last year the airline operated 3,446 flights in total on this route and carried 277,000 passengers, reports de Volkskrant.

Only 20 per cent of KLM’s passengers took the train even though Thalys’ schedules are competitive with air (journey time Brussels Midi to Schiphol is 93 mins) when check-in times, ground transfers etc are included.

So why does KLM persist?

KLM is a sixth-freedom airline. It needs transfer passengers to fuel its large network.

Amsterdam-Brussels is patronised by many high-fare business travellers, and therefore is too valuable to sacrifice.

KLM itself confirmed to de Volkskrant that almost all travellers on are transferring at Schiphol to onward destinations.

Its decision to continue with its monopoly route was criticised by Dutch MPs last March, who voted to scrap the flights.

Transport Minister Cora van Nieuwenhuizen said that such a move would free up space at Schiphol for more useful flights.

But at the end of the day, the minister has admitted that she cannot force airlines to give up destinations.