During the last several years, senior Navy officials have testified before Congress on the effects of shortages in training resources on the readiness of aviation units. This report examines one of these resources--ordnance for air-to-ground training--to assess the potential for enhancing Navy and Marine Corps tactical aviation unit readiness by improving training ordnance management. The availability of Navy and Marine training ordnance depends on an accurate requirements determination process, a procurement program that supports identified needs, and an allocation process that puts the right amount of ordnance where it is needed for training. The Navy program has problems with all three of these elements. Neither the Navy nor Marine Corps provides request data that reflect the training needs identified in its training instruction. Although both services have linked their ordnance requirements to readiness in their training instructions, neither services' request indicates that its instruction serves as the basis for identifying its needs. GAO believes each service has the knowledge and ability to develop more accurate and justifiable training ordnance requirements. Training ordnance shortages limit the amount of training and exercises aircrews can carry out and reportedly affect their proficiency in certain tasks. The shortages also extend the period of time when units are at lower readiness levels and force them to make a last-minute "rush" to achieve readiness just before deployment. This increases the risk that units may not be sufficiently prepared if they suddenly are needed for an unexpected deployment.