Hoping to fly to your summer vacation? Plan on opening your wallet a little, perhaps a lot, more than a few months ago. According to the fare comparison site Hopper, the average round trip ticket is up more than 30% from a year ago, to now just over $330. But that may seem cheap if you’ve been searching for summer flights, where many are $400 or more. The biggest reason for rising fares right is the dramatic jump in oil, and therefore, jet fuel prices. Delta says jet fuel is costing the airline 33% more than at the end of last year, so it recently announced a 10% across-the-board fare hike to cover those costs.