TD,
Probably neither,
The safety case should reflect the level of risk. There may well be a risk of loss of aircraft through fire. The safety case should should identify the hazards leading to such an accident and show that such hazards have been mitigated to an acceptable level (As Low As Reasonably Practical). Such an level doesn't mean no risk though. The problem though, is for those risks which are not Intolerable, but also not Broadly Acceptable. There will always be debate over such Tolerable risks because of all the factors and stakeholders views that a duty holder is trying to balance when deciding whether to accept such a risk.
sw