a method and a manufacturing line for manufacturing wind turbine blades having a composite shell structure comprising a matrix material and a fibre reinforcement material by use of a resin transfer moulding process . the method comprises a manufacturing line , where wind turbine blades are formed in a number of moulds . each number of moulds comprising at least a first mould part comprising a first mould cavity . the manufacturing line further comprises a gantry means movable along the manufacturing line . the method comprises the following steps : a ) arranging fibre reinforcement material in the first mould cavity of a first mould using the gantry means , b ) moving the gantry means along the manufacturing line to a second mould , c ) supplying curable matrix material into the first mould cavity of the first mould , while substantially simultaneously arranging fibre reinforcement material in the first mould cavity of a second mould using the gantry means . the manufacturing line comprises a plurality of moulds for forming wind turbine blades . each of the number of moulds comprising at least a first mould part comprising a first mould cavity .