Definition
A ground-based air traffic system that delivers routine clearance and advisory information to aircraft via text-based data link instead of voice radio at terminal airports. TDLS commonly provides Pre-Departure Clearances (PDC), Digital ATIS (D-ATIS), and taxi instructions, sending the information directly to the aircraft's onboard data link equipment or to the operator's dispatch system for delivery to the crew.
Plain English
A system at busier airports that sends clearances and airport information to the cockpit as text messages, so pilots don't have to copy everything by listening on the radio.
Context Anchor
You may see TDLS mentioned in ATC, clearance delivery, pre-departure clearance, or digital airport information discussions at larger airports.
Derivation
"Terminal" refers to the airport area where arrivals and departures happen, as opposed to en route airspace. "Data link" means a digital communication channel between the ground and the aircraft. So the name describes exactly what it is: a data link used at terminal airports.
Why Pilots Care
It reduces radio frequency congestion, provides a written record of instructions, and lowers the chance of misheard clearances.
Intuition Check
Do not read “Terminal” here as a passenger building or a computer screen. In this term, “terminal” means the airport-area part of the air traffic system, especially the airspace and facilities near an airport.
Example Sentence 1
We picked up our clearance through TDLS before calling for pushback, so the frequency stayed clear for other crews.
Example Sentence 2
Instead of listening to the voice ATIS, the pilot pulled the current weather information over TDLS.