Showing improved performance industry-wide, U.S. airlines lost fewer bags in 2017. According to the annual Airline Quality Rating, released Monday morning, the rate among the 12-largest U.S. airlines for mishandled bags decreased to 2.46 per 1,000 passengers in 2017, down from 2.70 in 2016. That's the industry's best-ever performance on that metric in the nearly 30-year history of the AQR. The study is compiled by Dean Headley, a marketing professor at Wichita State University, and Brent…