Which of the following is a limitation of a sport pilot certificate?

A significant limitation of a sport pilot certificate is that the holder cannot operate outside the United States without specific authorization from the appropriate aviation authorities. This restriction is primarily due to the varying regulations and standards that exist in different countries concerning pilot certifications and aircraft operations. Each nation has its own regulatory framework, which may not recognize a U.S. sport pilot certificate. As a result, pilots must ensure they comply with international aviation laws and often need additional certifications or validations to operate in foreign airspace.

The other options present various privileges and limitations that do not align with this specific restriction. For instance, the ability to fly solo at night with a logbook endorsement reflects an additional endorsement that expands the privileges beyond basic sport pilot operations but is still within the limits of what a sport pilot can achieve. Similarly, carrying more than one passenger with restrictions also implies a limitation that can be lifted with certain exceptions based on the aircraft's capabilities and regulations. Lastly, the statement regarding flying any aircraft with a valid license does not accurately reflect the limitations of a sport pilot certificate, which specifically restricts the pilot to operating light-sport aircraft only. Understanding these distinctions helps clarify the specific limitations imposed on sport pilots.