The National Transportation Safety Board kicked off two days of investigative hearings Tuesday in Washington as part of the agency's investigation into Louisville's deadly UPS plane crash.

UPS announced Tuesday that its fleet of McDonnell Douglas MD-11 cargo planes are now officially retired two months after the fiery crash in Louisville that killed 15 people.

Mayor Craig Greenberg said Monday some areas where the crash happened near Louisville's airport had oil that was up to three or more feet deep following the crash.