 fine particle pollution was at least 20 times worse than usual in some areas of Southern California. For NPR News, I'm Erin Stone in Los Angeles. With the nation's airlines seeing an uptick in travel, it's perhaps not surprising the number of complaints is also on the rise. The Transportation Department says it received nearly 97,000 passenger complaints last year, up from around 83,000 the previous year. More than two-thirds of the complaints filed dealt with domestic carriers.