Army fielding is the process by which new equipment is distributed to soldiers either at dispersed units at homeland or at theatre of operations (J.D. Carter, SIEDS IEEE, 2007). Minimization of personnel, space and time resources are of utmost importance for improving the supply chain management system and the fielding of the necessary equipment at the theatre of operations. The equipment is stored in central warehouses where frequent and large orders of miscellaneous items are received each day. The items have to be picked from specific location within the warehoused then consolidated and finally dispatched. The most common type of warehouse is divided into parallel aisles between multistore storage racks. The order picking personnel walks or drives along the aisles to pick items from storage. They can change aisles at a number of cross aisles, which are usually located at the front and the back of the warehouse, but in some cases additional cross aisles are located at positions in between. In this paper, optimal routing of order pickers in parallel aisle warehouses is formulated as a Travelling Salesman Problem (TSP). A Threshold Accepting meta-heuristic algorithm is proposed next for the solution of the problem. The proposed method is tested on a large set of randomly generated instances and is compared favourably to other methods that can be found in the literature. Moreover, the proposed method is implemented for the solution of a number of instances obtained during the operation of a real warehouse. The method produces better results compared to the method used in practice and it is shown that the warehouse operations can be significantly benefited.