Hello all- I am a relative newcomer to miles and upgrades. I am in the very early stages of planning our next family trip to Europe and I had a couple of questions: 1. When booking seats on an airline, what are the advantages to booking seats in certain fare classes? If you're paying more for a seat in coach in a different fare class, what is the reasoning behind it? 2. And this may be related to #1, what does it mean when your seats are "upgradeable"? Is that a free move to the next class? 3. Open jaw flights- if I'm using Delta, for example, can I make flight plans using open jaw plans? If I want to fly to Spain and fly home from Italy, what is the most economical way to do it? I won't be using miles for this trip, so I really want to make best use of every travel dollar. Your help is greatly appreciated.