A transient air flow simulation model of a typical aircraft vacuum waste system was correlated against limited airplane test results. The model was used to analyze a variety of conditions which could be encountered while in service. The analysis showed that simultaneous flush and a sequential flush of all the lavatories will not have adequate air flow. However, both flight tests and in-service performance to date indicate no problems with inadequate air flow. It is also improbable that simultaneous or sequential flushing will each occur repeatedly in short time intervals. Thus, continuous inadequate airflow will not exist. Therefore, no changes to the system are required.