1. A reservation method operating on a distributed reservation system including a plurality of Open Back End servers (OBE), each OBE being adapted for providing a service, for controlling consistency of PNR record during a user transaction across at least two OBEs, the method including the steps of: a reservation interceptor module, receiving a user request comprising a data structure including the request for at least one service and reference to a PNR record; the reservation interceptor module enriching the data structure with information including the content of PNR record; the reservation interceptor module forwarding the enriched data structure to a first at least one OBE according to the at least one service requested in the user request; responsive to the first at least one OBE returning an up to date version of the enriched data structure, the reservation interceptor module forwarding the enriched data structure in turn to other OBEs until all requested services included in the user request have been provided; and returning a response associated to the at least one service requested by the user.