This paper presents modeling of miles-in-trail passback restrictions for use in air traffic management. Generally, FAA managers employ miles-in-trail as a traffic management initiative when downstream traffic congestion at airports or in sectors is anticipated. In order to successfully implement the miles-in-trail at airspace fixes or navigational aids, it is desired that restriction values be computed for passing back to upstream facilities at specific boundaries. This paper presents a model which can be used for that purpose. This model improves on a previous version using traffic manager feedback resulting in significant improvement in guidance. The modeling approach is described along with lessons learned and improvements made during model development. Results for two sample traffic and one real traffic scenarios are presented. Additional operational considerations required by the traffic managers to implement the passback restrictions, namely maximum ground delay and absorbable airborne delay are incorporated in the model. A main result of this research is that absorbing small amount of ground and airborne delays are sufficient to handle the imposed constraint. Another finding is that implementing the passback restrictions provides the traffic managers ways to alleviate traffic constraints to help reduce excessive airborne delay for current traffic conditions.