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

// preload images for navigation
  function preloadImages() {
  var aircraft_maint = newImage("images/navigation/aircraft_maint.gif");
  var aircraft_maint_red = newImage("images/navigation/aircraft_maint_red.gif");
  var aircraft_management = newImage("images/navigation/aircraft_management.gif");
  var aircraft_management_red = newImage("images/navigation/aircraft_management_red.gif");
  var aircraft_parts = newImage("images/navigation/aircraft_parts.gif");
  var aircraft_parts_red = newImage("images/navigation/aircraft_parts_red.gif");
  var aircraft_sales = newImage("images/navigation/aircraft_sales.gif");
  var aircraft_sales_red = newImage("images/navigation/aircraft_sales_red.gif");
  var avionics_services = newImage("images/navigation/avionics_services.gif");
  var avionics_services_red = newImage("images/navigation/avionics_services_red.gif");
  var certificates = newImage("images/navigation/certificates.gif");
  var certificates_red = newImage("images/navigation/certificates_red.gif");
  var charter = newImage("images/navigation/charter.gif");
  var charter_red = newImage("images/navigation/charter_red.gif");
  var company_info = newImage("images/navigation/company_info.gif");
  var company_info_red = newImage("images/navigation/company_info_red.gif");
  var components = newImage("images/navigation/components.gif");
  var components_red = newImage("images/navigation/components_red.gif");
  var contact_us = newImage("images/navigation/contact_us.gif");
  var contact_us_red = newImage("images/navigation/contact_us_red.gif");
  var fbo_services = newImage("images/navigation/fbo_services.gif");
  var fbo_services_red = newImage("images/navigation/fbo_services_red.gif");
  var home = newImage("images/navigation/home.gif");
  var home_red = newImage("images/navigation/home_red.gif");
  var oem_affiliates = newImage("images/navigation/oem_affiliates.gif");
  var oem_affiliates_red = newImage("images/navigation/oem_affiliates_red.gif");
  var testimonials = newImage("images/navigation/testimonials.gif");
  var testimonials_red = newImage("images/navigation/testimonials_red.gif");
}