Abstract : The U.S. Navy trains its surface combatant ship crews through a combination of shore-based, onboard pier-side, and underway training. Much of this training has traditionally involved significant periods of underway time, which allows units to achieve required certifications and readiness levels. Underway training is expensive, however, because fuel and consumables are expended while a ship is underway; wear and tear on operating equipment also drive up maintenance costs. One day's worth of fuel for one surface combatant costs approximately $40,000. Tight budgets and increasing recapitalization costs have forced the Navy to examine various methods to reduce the annual operating costs of the fleet. Technological improvements have increased the fidelity and realism of simulators, and simulation is being used more widely for training within the U.S. Navy. Although the Navy's surface combatant community currently uses simulators in its training regimen, an increased use of simulation could improve training efficiency, sustain training readiness, and potentially reduce underway days. This research identified underway training requirements for surface combatants for unit-level training (ULT), the number of underway days required to accomplish that training, and where credit for meeting training requirements through the use of simulation is currently granted. In addition, it identified which training requirements can only be completed underway, which can be completed in port without simulation, and which can be completed in port via simulation. The authors then surveyed available simulation technologies to determine if they could be substituted for training that is currently being performed underway. The research focused on the DDG-51 Arleigh Burke-class surface combatants because the DDG-51 class has the greatest number of ships in the surface combatant fleet, providing a large data set for an analysis of training exercises performed.