Under threat of indictment, American Airlines pleaded guilty yesterday to illegally storing hazardous waste at the Miami airport and transporting hazardous and poisonous materials improperly on its passenger jets for the last five years,. The company will pay $8 million, the largest environmental fine ever levied against an airline, as well as make changes to ensure its passengers are safe and apologize in a full-page ad in the Miami Herald. An investigation of the company began in 1997, after an illegally marked, undocumented bag of pesticide broke open in the cargo hold on a flight to Ecuador, releasing fumes that forced the evacuation of 53 passengers and crew members. In other news about naughty big companies, the EPA is seeking to fine Wal-Mart $5.6 million for allegedly violating storm water permits in three states.