What Is ATD? Definition & Meaning in Aviation
ATD (actual time of departure) is the time an aircraft really left, usually when it pushed back from the gate or took off.
In plain language
Different airlines use different definitions, so ATD can mean off-blocks (leaving the gate) or wheels-up.
Example
A flight with an STD of 09:30 that pushes back at 09:50 has an ATD of 09:50.
Why it matters
The ATD marks when a flight really began. Because some airlines record it at pushback and others at takeoff, two sources can show different departure times for the same flight.