In 2007, the nation's four largest rail companies were sued over conspiring to fix prices. The litigation is still ongoing, and a class of plaintiffs was certified last year. So it is a class action. Recently, the rail companies tried to decertify the class. The case illustrates the tendency of defendants in a class action to seek quick settlement, because there is so much risk in taking a class action to trial. If the defendant in a class action loses, the potential amount it would have to pay could reach 10-figures or more.
The process of certifying a class is very complex. So, once a class is certified, it is rarely decertified.