WXI  WXR.Indicator 
WXP  Weather.Radar.Panel 
WXR  Weather.Radar.System 
WWW  World.Wide.Web 
WYPT  Waypoint.Altitude 
XA  ARINC 
X-BAND  The frequency range between 8000 and . 
12500.MHz 
XB  International.Air.Transport.Association.(IATA) 
X-Channel  A.DME.channel..There.are.126.X-channels.for. 
DME operation. For the first 63 channels, the 
ground-to-air frequency is 63 MHz be low the 
air-to-ground frequency. For the second 63-X 
Channels the ground-to-air frequency is 63 MHz 
above the air-to-ground frequency. 
XCVR  Transceiver 
XFR  Transfer 
XID  Exchange Identification 
XLS  Cross-side 
XLTR  Translator 
XM  External.Master 
XMIT  Transmit 
XML  eXtended.Markup.Language 
XMTR/RCVR  Transmitter/Receiver 
XPD  ATC.Transponder.(also.XPDR,.X.PNDR,.TPR) 
XPDR  Transponder 
XPTR  Cross Pointer: The flight director command bars. 
Pitch.command.is.shown.with.vertical.motion.of. 
the.horizontal.bar.and.roll.command.is.shown. 
with.lateral.motion.on.the.vertical.bar. 
XS  SITA 
XSIDE  Cross-side 
XTI  X/Open Transport Interface 

XTK Crosstrack.(crosstrack.error)
XTP Express.Transfer.Protocol
Yagi Antenna An.antenna.with.its.maximum.radiation.parallel.

to.the.long.axis.of.its.array,.consisting.of.a.driven.
dipole, a parasitic dipole reflector, and one
parasitic.dipole.director.or.more. YAW Refers.to.movement.about.the.vertical.axis.of.the.
aircraft
YSAS Yaw.Stability.Augmentation.System
YD Yaw.Damper
Z ( 1 ) Refer to reflectivity factor .
(.2.).Zulu.(GM.Time)
ZDE Zone Distribution Equipment
ZFW Zero.Fuel.Weight
Z-Marker A.marker.beacon,.sometimes.referred.to.as.a.
station locator, that provides positive identification
to.the.pilot.when.the.aircraft.is.passing.directly.
over a low-frequency navigation aid.
Z Zulu.Time