I would like a system where the airline had to declare the type of aircraft used on the flight at the time of booking. If at the time of departure the aircraft model actually use for the flight is different then the passenger must on request be repaid the entire value of the ticket.

This means that there is no (financial) pressure on the passenger to fly on an aircraft they do not trust.

Currently the live-or-die risk devolves to the passenger and they have no direct say in the choice of aircraft: after ticket purchase they are left with a take-it-or-leave-it proposition.

This system might force airlines to think much much harder when making their aircraft purchasing decisions.

Just because the aircraft is certified will no longer amount to adequate commercial due diligence.

An airline which wants to protect its revenue will now need to deep-dive into the manufacturers quality procedures themselves.

Otherwise their customers can vote with their feet, at no financial cost, any time prior to departure.