Queues Up All Requests That Use The Same Session ID

It seems to me that ASP.net queues up all requests that use the same Session ID. Let's say you've got 3 pages. Default.aspx

protected void Page_Load(object sender, EventArgs e)
{
Session["asdf"] = "LOLZ";
}

Hitting this page would obviously create a new session if one doesn't exist.

X-AspNet-Version: 2.0.50727
Set-Cookie: ASP.NET_SessionId=ibjphuv0aiafqi453tyze345; path=/; HttpOnly

Then you hit Hang.aspx

protected void Page_Load(object sender, EventArgs e)
{
Thread.Sleep(10000);
}

And immediately after you hit any other page that this session ID would be passed to, doesn't matter if it does anything, let's call it Test.aspx. The sequence for loading is like so.

Request Timeline
"GET /" |*|
"GET /Hang.aspx" |******************************************|
"GET /Test.aspx" |**************************************|

I guess my question is how do I disable this feature. I understand it's useful to have so that session state can be more predictable, however in my case a long running reports page load is killing users' ability to multitask.