Reducing the transmission time for a flow network is an essential task. The quickest path problem thus arises to find a path with minimum transmission time. More specifically, the capacity of each arc in the network is assumed to be deterministic. Nevertheless, the capacity of each arc is stochastic due to failure, maintenance, etc. Such a network is named as a stochastic-flow network. Hence, the minimum transmission time is not a fixed number. We extend the quickest path problem to a system reliability problem that d units of data are required to be sent from the source to the sink under the time threshold T. The possibility to fulfill such requirements is named as the system reliability. In particular, the data can be transmitted through two disjoint minimal paths simultaneously. A simple algorithm is proposed to generate all lower boundary points for (d,T) and the system reliability can be subsequently computed in terms of such points. Moreover, the optimal pair of paths with highest system reliability can be further obtained.