You need public accessor methods such as getName, getID that simply return the values of those private variables. That way you allow other classes to get the values in a controlled way, but not to change or corrupt them.
Similarly you can create public setID etc methods if you want other classes to be able to change some of those values.
In your case, where presumably every Passenger has an ID and a name, which never change, you should consider having a public constructor that requires those values as parameters to create the Passenger object, and not having any set methods.
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...