This doesn't matter. If airlines go under, they go under. The airline industry is what my WWS micro-econ professer classed as "easily contestable." Assuming that other airlines haven't tied up all airport gates (e.g., haven't been allowed to lock up all gates in pursuit of monopoly), all an investor (or group of investors) has to do is buy some planes, hire some staff (pilots, attendants, mechanics, etc.). In other words, if/when demand returns, airlines will be established...at least to the extent that it's profitable. Now, fares may be higher, and as a result, flying may become less common "just for fun," but that's not necessarily a bad thing. A real carbon tax on jet fuel, to discourage casual air travel, would also be... interesting?... given the extent to which the airline industry is responsible for atmospheric CO2 increase.