The average total cost is the total costs (both fixed costs and variable costs) divided by the total quantity produced. It is used to determine the breakeven price, which is the minimum price that if used, the company will have no gains and no losses.

Air Traffic Control (ATC) is the "invisible hand" that ensures the safety and orderly flow of global aviation. For pilots, ATC helps figure out separation, routing, and sequencing. Specifically, controllers provide "Separation Minima" to ensure planes do not collide in mid-air or on the runway. They help figure out the most efficient flight path based on current weather, turbulence reports, and "restricted" military airspace. During the approach phase, ATC helps figure out the "landing sequence," telling pilots exactly when to slow down, what altitude to maintain, and which runway is "cleared for landing." In 2026, with the integration of NextGen and CPDLC (Controller-Pilot Data Link Communications), ATC also helps figure out fuel-efficient "Continuous Descent Approaches" (CDAs), which reduce noise and carbon emissions. Essentially, while the pilot "drives" the plane, ATC acts as the "GPS and Traffic Cop" combined, managing the complex 3D chess board of the sky to ensure everyone gets to their destination without incident.