Travel Recommendation: Belgrade, MT to Denver, CO
  Air
      - Companies: Delta Air Lines, United Airlines, American Airlines
     - Duration: Approximately 6 hours (including layover)
     - Distance: Approximately 1,000 miles (1,600 kilometers)
     - Costs: R3,500 - R5,000 [varies based on booking class and time]
     - Roads/Routes: Not applicable
   
  Pro Tip: Book your flight at least 2-3 months in advance for better rates and try to choose flights with shorter layovers to save time.
    Ground Transport
      - Mode: Long-distance bus or car rental
     - Companies: Greyhound, FlixBus, Enterprise Rent-A-Car
     - Duration: Approximately 16-18 hours (by bus); 13-15 hours (by car)
     - Distance: Approximately 900 miles (1,450 kilometers) by road
     - Costs: Bus fare - R1,200; Car rental - R2,500 (including fuel costs)
     - Roads/Routes: I-90 E and I-25 S
   
  Pro Tip: For a car rental, download offline maps for navigation and ensure you have a roadside assistance plan just in case of emergencies.
    Recommendation
  For a smooth and efficient journey, I recommend flying as it significantly reduces travel time. However, if you prefer the road trip experience, opt for a rental car to enjoy the scenic views along I-90 E and I-25 S while stopping at interesting landmarks. Always check for the latest travel advisories and weather conditions before embarking on your journey.