This even might be justified because the airport rendered certain services on request of the airline. From a less legal and more philosophical viewpoint you might wish to ask:

Who has to take the risk?

In the first instance: The person "deciding" to pass away. If I were the carrier, I would seek my expenses from this person (or the estate). The airport did not act for the person passing away but for the airline and on request of the airline. So the airport should go after the airline and the airline seek refund from the estate (or as somebody brought forward: his medical insurance).

And the other pax: Well, they just had bad luck. The person passing away just passed away. The other pax did not do anything, rendered no services but just suffered. But they suffered because the poor guy died and from what we read he died not voluntarily (in such circumstances you might be able to hold the estate liable, however "good luck"). They were "victims" of an act of God.