If statement does not work

programming flash
1

the problem is that for some reason my if statement doesn’t work

if( key.isDown( Keyboard.UP ) ) 
                                {
                                        ship.thrust-=.02;
                                     ship.gravity=-.050;
                                     trace("up");
                                     if(shipLanded=true)
                                     {
                                    
                                         removeChildFunc();
                                     }
                                    
                                      
                                }

once the up key is pressed the button is to be removed IF shipLanded is true. so it should just bypass removeChildFunc.

after the above code i have

 ship.moveShip();
                ship.rotateShip();
                moveRocks();
                land();
               [U]** trace("shipLanded= " + shipLanded );**[/U]
                 healthBar.subtractHealth(ship.damageAmt);
                 checkDeath();
                ship.damageAmt=0;

then way down at the bottom i have my removeChildFunc()

public function removeChildFunc():void
            {
                trace("removing child");
                trace(asBaseScreenButton.parent);
                removeChild(asBaseScreenButton);
            }

and here’s my output

shipLanded= true
shipLanded= true
shipLanded= true
up
removing child
[object PlayScreen]
shipLanded= false
up
removing child
null
ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.
at flash.display::DisplayObjectContainer/removeChild()
at PlayScreen/removeChildFunc()[C:\Documents and Settings\rob\Desktop\AS3\Projects\AsteroidSupply\Classes\PlayScreen.as:457]
at PlayScreen/upDate()[C:\Documents and Settings\rob\Desktop\AS3\Projects\AsteroidSupply\Classes\PlayScreen.as:162]

that shipLanded =false should preclude the removing child and the null and the error???