I dont know the history of this but you can open HTML pages within an AIR application. This control is not available in Flex though and I would wish to have it. However the way to do this in Flex is mentioned in the comments below.
I can already see the benefits of this. I have not tried it out myself but soon I will try it. You need to use an HTML control to do this.
For a user interacting with an HTML control, the experience is similar to using a web browser with only the content window and no menu bar or navigation buttons. The HTML page content displays in the control. The user can interact with the content through form fields and buttons and by clicking hyperlinks. Any action that normally causes a browser to load a new page (such as clicking a link or submitting a form) also causes the HTML control to display the content of the new page and changes the value of the control’s location property.