function newImage(arg) {
	if (document.images) {
		rslt = new Image();
		rslt.src = arg;
		return rslt;
	}
}

function changeImages() {
	if (document.images && (preloadFlag == true)) {
		for (var i=0; i<changeImages.arguments.length; i+=2) {
			document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
		}
	}
}

var preloadFlag = false;
function preloadNavImages() {
	if (document.images) {
		navHome_over = newImage("main_images/navHome-over.gif");
		navNotice_over = newImage("main_images/navNotice-over.gif");
		navWings_over = newImage("main_images/navWings-over.gif");
		navAirfield_over = newImage("main_images/navAirfield-over.gif");
		navAircraft_over = newImage("main_images/navAircraft-over.gif");
		navContact_over = newImage("main_images/navContact-over.gif");
		preloadFlag = true;
	}
}