A conditional purchase offer (CPO) management system is disclosed for receiving CPOs from one or more customers, such as airline passengers, and for evaluating the received CPOs against a number of CPO rules defined by a plurality of sellers, such as airlines, to determine whether any seller is willing to accept a given CPO. A CPO is a binding offer containing one or more conditions submitted by a customer for purchase of an item, such as airline travel, at a customer-defined price. A CPO rule is a set of restrictions defined by a given seller, such as an airline, to define a combination of restrictions for which the seller is willing to accept a predefined price. The CPO rules may be securely stored by one or more servers. The CPO management system permits a seller to correct for forecasting errors, if necessary, or other competitive forces which have produced excess capacity, by providing inventory for sale to CPO customers.