To get from Terminal C to Terminal F at Philadelphia International Airport (PHL) without exiting security, you should use the free airside shuttle bus. The shuttle stop in Terminal C is located near Gate C16. These buses run frequently (usually every 5-10 minutes) and take you directly to Terminal F, which is located at the far end of the airport complex. You can also walk between the terminals, but it is a significant distance; walking from Terminal C to Terminal F can take 20 to 30 minutes as you have to navigate through the connectors. If you are outside security (landside), you can take the Economy Parking Shuttle or a terminal-to-terminal shuttle, but you will have to go through the TSA security checkpoint again at your destination terminal. For most passengers with a tight connection, the airside shuttle from C16 is the most efficient and stress-free option.