In an effort to keep more ships at distant stations longer and at less expense, the U.S. Navy is experimenting with returning the crews, but not the ships, when a crews six month tour of duty in a distant area is completed. After 18 months, the ship itself would return to its home port for maintenance. But the "Sea Swap" program would save up to 90 days of time normally spent getting the ship from its home port to its distant operating area. The program is an experiment, mainly because of uncertainty about how sailors will react to taking over another crew's ship like this. A similar program has worked with SSBN (ballistic missile subs) for decades, where two crews were used to keep the SSBN at sea for the maximum amount of time. The success of the SSBN use of "blue" and "gold" crews for one ship is providing guidelines for the "Sea Swap" experiment. Warplanes have long used multiple crews for a single aircraft, since the equipment can take a lot more use than the people that operate them. With ships becoming more automated, and crews smaller, the concept of having multiple crews for surface ships, as well as SSBNs, is becoming more practical. "Sea Swap," however, will have the crew that is relieved dispersed to new individual assignments once it returns to the United States. It is feared that regularly forming new crews for assignment to ships will result in lower morale and crews that won't work together as well as a crew that has been together for a long time.