Not quite airy, but close. I combined several recipes to get a loaf like I'd buy in the store. The sour flavor will depend on what type of starter you use, and how strong it is. I use a 2 week old starter, that was frozen and thawed the night before- it had a mild flavor. I basically used Recipe #13750 with milk instead of water. Serve warm with homemade Recipe #182268 for a real treat. I suppose this could be made in a bread machine - but I haven't tried it. I find it very relaxing to mix and knead a loaf of bread by hand, and then to make butter while its baking :-) I think my loaf pan must have be over-sized, because this recipe seems to make two loafs. I like everything sweet, including my sour dough bread. If you prefer less sugar, just use a tablespoon or two to proof the yeast.