When I make an unquilted cotton jacket, it is sometimes necessary to add some body.  I don't always like to interface the fabric and underlining is a more breathable choice.  Cut the jacket body pieces from a lightweight fabric such as a poly/cotton batiste (I don't usually underline sleeves).  Place the underlining on the wrong side of the jacket pieces and press.  Pin or baste the underlined pieces and assemble the jacket, treating the underlined pieces as one piece.  Line the jacket as usual.