U.S. airlines took a beating in early 2018 amid several high-profile clashes with disgruntled passengers, and they appear to have responded accordingly. Complaints lodged against major U.S. air carriers hit a five-month low of 635 incidents in October, the most-recent reporting period available, and were down roughly 12 percent on a per-passenger basis when compared to the same 31-day span in 2017.