Usually tickets purchased with a credit card (but not debit cards) are protected, although personal/consumer cards might have better protections than business or corporate cards. There can also be protections if the ticket was purchased through a recognized travel agent.

An obvious problem is that the refunds based on these protections can take time while the traveller must purchase a new and sometimes last minute or one way expensive ticket. Space on other carriers can be very limited.

In some cases, other carriers have announced that they will accept tickets from the defunct airline on a space-available or standby basis, but they can have little incentive to do so. It's also harder to have this work with electronic tickets versus the old paper tickets.