In high-speed and high-capacity packet switches, system reliability is critical to avoid the loss of a huge amount of information and to avoid re-transmission of traffic. We propose a series of concurrent fault detection mechanisms for a multiple-plane crossbar-based packet switch. Our switch model, called the m + z model, has m active planes and z spare planes. This switch has distributed arbiters on each plane. The spare planes, used for substitution of faulty active ones, are also used in the fault detection mechanism, thus providing sufficient data redundancy for fault detection and location. Our detection scheme is able to detect a single fault in one time slot without increasing transmission overhead. The proposed schemes can be used for switches with different numbers of active planes and the number of spare planes needed for fault detection is small.