In ios Scroll bars in iframes are removed and render them as blocks. What I did for this solution is wrapping the Iframe inside a div and let the Iframe expand according to
<div id="myIframeParentDiv" class="myIframeParentDivClass">
<iframe style="z-index:2000" id="myIframe" width="100%" height="100%" src="" frameborder=0 ALLOWTRANSPARENCY="true" >
<p>Booking Engine error! your browser does not support iframes.</p>
</iframe>
</div>
STYLES
#myIframeParentDiv{
height: 100%;
width: 100%;
overflow:auto;
-webkit-overflow-scrolling: touch;
}