In addition to being almost guaranteed to secure ongoing US DoD contracts for military air-to-air refueling using the "probe and drogue" method, the ability to carry a mixture of passengers and cargo pallets and also conduct air-to-air refueling, makes the Tristar ideal for contracts for supporting cross-Atlantic or cross-Pacific deployments of fast jets for air forces who attend RED FLAG exercise at Nellis AFB or for deliveries of new aircraft from the US to overseas customers.

See this photo showing full-size cargo door open:

https://i2.wp.com/www.aeroresource.co.uk/wp-c...Buckle.jpg