Of course, you should not miss Jiuzhaigou Scenic Area, Chengdu Panda Breeding and Research Center , Huanglong Scenic and Historic Interest Area. Then you could also go to visit Sanxingdui(Three-Star Piles) Museum, Huanglongxi Ancient Town and Mt. Qingcheng. As to the airfare from Chengdu to Jiuzhaigou, it is hard to evaluated it since the fare changes much. You could check the following website to find the details: https://www.travelchinaguide.com/china-flights/ .