Definition
An air traffic control decision-support tool that helps controllers sequence and space arriving and departing aircraft within terminal airspace. TSAS extends time-based metering into the terminal environment, generating advisories that allow controllers to merge arrival streams, manage runway demand, and integrate area navigation (RNAV) and required navigation performance (RNP) procedures with conventional traffic.
Plain English
A controller tool used near busy airports that calculates the best order and spacing for arriving and departing aircraft, so traffic flows smoothly without bunching up or leaving gaps.
Context Anchor
Seen in AIM and air traffic control automation discussions. Pilots normally experience TSAS indirectly through controller instructions such as speed changes, headings, or other arrival instructions.
Derivation
Terminal refers to the airspace surrounding an airport (as opposed to en route). Sequencing means putting aircraft in order. Spacing means setting the distance or time between them. Together the name describes exactly what the tool does: orders and separates aircraft in the terminal area.
Why Pilots Care
It reduces delays, fuel use, and the need for holding while keeping safe separation on approach.
Intuition Check
Terminal does not mean the passenger building here; it means the airspace around an airport. Sequencing and spacing mean setting the order of aircraft and the gaps between them, not assigning gates or parking spots.
Example Sentence 1
Approach control was using TSAS to sequence the arrival stream, so we received a speed reduction about 30 miles out.
Example Sentence 2
TSAS recommendations allowed the tower to land more aircraft per hour during the evening rush.