This paper presents analysis of five airspace tube structures; three of which were previously defined and two new designs that were generated for this research. Five metrics to characterize the performance of these tubes are described. The metrics address the spatio-temporal utilization, frequency and angles at which aircraft cross tubes, along with separation of aircraft with and without tubes. All of the designs were incorporated in a common simulation platform for evaluation. The results indicate that current designs of tubes have low utilization and improvements are needed for additional benefits. Other structural parameters for consideration in future designs are presented along with visualization of a simple three-dimensional tube network.