Cruise speed refers to the constant speed at which a vehicle, such as an aircraft or a ship, travels during the majority of its journey. This speed is typically chosen for efficiency, balancing fuel consumption and travel time. For example, commercial airliners often cruise at altitudes where they can maintain optimal speeds while minimizing drag. In aviation, cruise speed is crucial for flight planning and safety. It allows pilots to estimate arrival times and fuel needs accurately. Different aircraft, like the Boeing 747 or Cessna 172, have specific cruise speeds that vary based on design and purpose, impacting their operational efficiency.