Average daily departures
Average daily departures means the average number of scheduled departures per day of air carrier aircraft computed on the basis of the busiest 3 consecutive calendar months of the immediately preceding 12 consecutive calendar months. However, if the average daily departures are expected to increase, then average daily departures may be determined by planned rather than current activity, in a manner authorized by the Administrator.
14 CFR § 139.5
The following are definitions of terms used in this part: