Hmm insurance is an interesting topic. If I recall correctly my airline used to split its insurance coverage. The hull insurance was kept in house and had its own contingent fund to fully meet its obligations. The labiality part was farmed out due to its potentially high payouts and was usually spread out among a multitude of insurance underwriters as no one insurance company would assume the risk alone. I understand this basket approach to insurance labiality is how all the majors do it.