var banner1 = new Image();
banner1.src = "images/banner_economy_on.jpg";
var banner2 = new Image();
banner2.src = "images/banner_student_on.jpg";
var banner3 = new Image();
banner3.src = "images/banner_biz_on.jpg";
var banner4 = new Image();
banner4.src = "images/banner_first_class_on.jpg";

//variable that will increment through the images
var next_wave_step = 1;
function mexican_wave() {
  var node;
  
  switch (next_wave_step) {
    case 1:
      node = document.getElementById ('slide4');
      node.src = "images/banner_first_class.jpg";
      
      node = document.getElementById ('slide1');
      node.src = "images/banner_economy_on.jpg";
      break;
      
    case 2:
      node = document.getElementById ('slide1');
      node.src = "images/banner_economy.jpg";
      
      node = document.getElementById ('slide2');
      node.src = "images/banner_student_on.jpg";
      break;
      
    case 3:
      node = document.getElementById ('slide2');
      node.src = "images/banner_student.jpg";
      
      node = document.getElementById ('slide3');
      node.src = "images/banner_biz_on.jpg";
      break;
      
    case 4:
      node = document.getElementById ('slide3');
      node.src = "images/banner_biz.jpg";
      
      node = document.getElementById ('slide4');
      node.src = "images/banner_first_class_on.jpg";
      break;
     
    case 5:
      node = document.getElementById ('slide4');
      node.src = "images/banner_first_class.jpg";
      break;
      
  }
  
  next_wave_step++;
  if (next_wave_step == 6) {
    next_wave_step = 1;
    window.setTimeout("mexican_wave()",5000);  // 5 sec
  } else {
    window.setTimeout("mexican_wave()",1000);  // 1 sec
  }
}