- Dacron Artificial fabric for light aircraft covering; trade name.
- DADC Digital air data computer.
- DADS Digital air data system.
- DARPA Defense Advanced Research Projects Agency (US) (briefly ARPA before February 1996).
- databus Electronic highway for passing digital data between aircraft sensors and system processors, usually MIL-STD-1553B or ARINC 419 (one-way) and 619 (two-way) systems.
- dB Decibel.
- DC Direct current.
- DECU Digital engine (or electronic) control unit.
- dem/val Demonstration/validation.
- derated Engine restricted to power less than potential maximum (usually such engine is flat rated, which see).
- design weight Different authorities have different definitions; weight chosen as typical of mission but usually much less than MTOW.
- DF Direction-finder, or direction-finding.
- DGAC Direction Générale à l'Aviation Civile. French certification authority.
- dihedral Upward slope of wing from root (or intermediate point) to tip.
- disposable load Sum of masses that can be loaded or unloaded, including payload, crew, removable equipment, usable fuel and other consumables; MTOW minus OWE.
- DME UHF distance-measuring equipment; gives slant distance to a beacon; DME element of Tacan.
- DoD Department of Defense.
- dog-tooth A sharp discontinuity in the leading-edge of a wing or tail surface resulting from an increase in chord (see also sawtooth).
- d.o.o. družba z omejeno odgovornostjo (Slovenian company constitution).
- Doppler Short for Doppler radar - radar using fact that received frequency is a function of relative velocity between transmitter or reflecting surface and receiver; used for measuring speed over ground or for detecting aircraft or moving vehicles against static ground or sea.
- double-slotted flap One having an auxiliary aerofoil ahead of main surface to increase maximum lift.
