Mobile ad hoc networks (MANETs) are becoming increasingly important. The most challenging issue in conjunction with MANETs is reliable routing, that is, the procedure that determines the trajectory of packets travelling over the network. The authors present a novel link availability-based routing protocol (LBRP) for MANETs. Compared with other routing protocols, LBRP takes unpredictable topology change and frequent link failure into account. Meanwhile, by a rough estimation of the distance between two adjacent nodes, the proposed approach is able to accurately predict link availability over a short period of time. Simulation results are given to verify the approach. This study could serve as groundwork for further MANET research, including analysing and optimising other network protocols. Reliable routing protocol can effectively improve the availability and reliability of upper layer services and quality of service.