Also, on people behaving rationally, which they usually do not. The difference between a cheapo and regular transatlantic flight is about 3-4 hundred bucks or less, depending on the season - a sum that is trivial vis a vis life and death issues, even for the poor. Otoh, in many parts of the world you do not have much choice, since none of the major airlines flies there.
But a broader point is that people's willingness to take risk is not rational in the necoclassical sense - but affected by a host of cognitive factors, especially framing, familiarity, etc. Risk taking or avoidance changes when the same outcome is stated in terms of potential loss or potential gain. People are willing to take a much higher risk in familiar settings (cf. driving in country roads which as almost twice as risky and driving on major highways, or driving which is several times as risky as flying, even the cheapo airlines). Then there is the endowment effect i.e. changes in the cognitive perception of value that depends on whether you own the object.
I think that people's willingness to fly cheapo airlines is affected not just by the price but also by the "folksy," "down to earth" or "fun" image these operators project.
Wojtek