The Pipeline and Hazardous Materials Safety Administration is required by law to respond to safety recommendations issued by the National Transportation Safety Board (NTSB), an independent federal agency charged by Congress with investigating significant incidents that involve hazardous materials. Recommendations usually address a specific issue uncovered during an investigation or study and specify how to correct the situation.

NTSB Classifications:

• OAR - Open Acceptable Response
• OAA - Open Acceptable Action
• OAAR - Open Acceptable Alternative Action
• OUA - Open Unacceptable Action
• OUR - Open Unacceptable Response
• UCL - Unclassified (until NTSB Classifies)

The items below are the currently open NTSB recommendations regarding aviation. To access downloadable letters containing  NTSB - PHMSA correspondence, click on the corresponding recommendation link and review "Related Downloads" located on the right-side menu.