-<Mission xmlns:z="http:..." xmlns:i="http:..." xmlns="http:..." z:Id="1">
    +<ActiveBullsEye z:Id="2" i:type="BullsEye">
    -<ActiveFlightPlan z:Id="7" i:type="FlightPlan">
        <AIRTAC z:Id="8"/>
        <Active>false</Active>
        -<Aircraft z:Id="9" i:type="a:Tanker" xmlns:a="http:...">
        -<ACColor xmlns:b="http:...">
             <b:A>255</b:A>
             <b:B>169</b:B>
             <b:G>169</b:G>
             <b:R>169</b:R>
             <b:ScA>1</b:ScA>
             <b:ScB>0.396755248</b:ScB>
             <b:ScG>0.396755248</b:ScG>
             <b:ScR>0.396755248</b:ScR>

XElement xdocument = XElement.load(filepath) //This works
XElement missionBlock = xdocument.Element("Mission") //(ERROR) This not get Mission tag

foreach( XElement acColor in missionBlock.Elements("ACColor") ) { (ERROR) Not found ACColor
    ...
}