C# - Adding User Control To Page Programmatically While Preserving Controls Already Present

I am trying to add a user control into a div at runtime. I can add the control no probelem but it overwrites the previous control added.Basically, I am trying to add passengers to a travel system - the passenger details are in the user control and I don't know in advance how many there will be. I have an add new passenger button which should append the new user control into the div without overwriting the previous passenger. The code is c#/.net 4. I have tried to save the control data into viewstate and re add it with the new one but that also doesn't work. Here is a snippet of the code I'm using

foreach (Control uc in p_passengers.Controls) {
Passenger p = uc as Passenger;
if (p != null) {
p.SaveValues();
}
}

however, p.SaveAs() (just writes the control values into ViewState) is never hit.