Unfortunately, flat tires are a fact of life in driving cars, and you as a traveler are responsible for a flat tire that occurs during the trip, as well as any related damage that may result from that flat or damaged tire.
However, the traveler will not be held financially responsible for replacing the tire if it is professionally documented that the flat is the result of a tire that was either 1) defective, 2) had been subject to excessive wear such that it was unsafe to be driven as of the start of the reservation, 3) was not properly inflated when the vehicle was provided to you, 4) had tread depth less than 2/32th of an inch, 5) had signs of dry rot, or 6) was more than 6 years old.
In all cases, the individual protection plan selected by each party would be in effect for the tire claim. E.g. If the traveler has selected premium, basic, or decline, the waiver from the protection package will apply. If the owner has selected premium, standard or basic, the relevant deductible will apply.
In the event of a flat, the traveler should look to a spare tire (our roadside service can dispatch a provider to help with this), and then coordinate with the owner to determine how to resolve the tire issue. If a repair is appropriate, that may be an effective way to go. If the sidewall is damaged or a repair is not possible, the renter is responsible for replacement of that tire (without any reduction or pro-ration based on mileage), but is not responsible for replacement of any of the non-damaged tires. The traveler needs to get the approval of the owner for a replacement tire, and must replace the tire with one of equal or greater quality.
If both the traveler and owner are unable to work it out as stated above, the individual protection plan selected by each party would be in effect as part of their damage claim.