Which method is safer for aircraft fueling operations at major air carrier airports?

Underground fuel systems are considered the safest method for aircraft fueling operations at major air carrier airports for several reasons. Primarily, these systems are less vulnerable to accidents and spills that can occur with above-ground systems. Being underground minimizes the risk of fuel leaks, which can pose serious hazards, including fire hazards and environmental contamination.

Additionally, underground systems are less susceptible to physical damage from vehicles or equipment operating in the airport environment. The protection offered by being buried underground makes these systems less likely to experience breaches due to impacts or weather-related events. Finally, underground fuel storage can also help maintain the fuel's temperature stability, reducing the likelihood of vaporization and ensuring fuel quality meets stringent aviation standards.

In summary, the design and placement of underground fuel systems significantly enhance safety during fueling operations compared to above-ground tanks, pipelines, or trucks, which have higher exposure to risks associated with accidents and environmental factors.