WASHINGTON (AP) — A collision between an American Airlines passenger jet and an Army helicopter near Washington, D.C., that killed 67 people brought renewed focus on the federal agency charged with investigating aviation disasters.

National Transportation Safety Board Chairwoman Jennifer Hommendy described the investigation into the crash Wednesday night as an “all-hands-on-deck event” for the agency during a news conference Thursday in which she appeared with members of the board and a senior investigator overseeing the probe.

Here are some things to know about the NTSB:

What does the agency do?

The NTSB is an independent federal agency responsible for investigating all civil aviation accidents as well as serious incidents in the U.S. involving other modes of transportation, such as railroad disasters and major accidents involving motor vehicles, marine vessels, pipelines and even commercial space operators.

“We’re here to ensure the American people that we are going to leave no stone unturned in this investigation,” Hommendy said, noting the probe is in the very early stages. “We are going to conduct a thorough investigation of this entire tragedy, looking at the facts.”

The agency has five board members who serve five-year terms and are nominated by the president and confirmed by the U.S. Senate.

How will the investigation work?

For the investigation into Wednesday’s crash, the NTSB will establish several different working groups, each responsible for investigating different areas connected to the accident, board member Todd Inman said.

Inman said those groups include operations, which will examine flight history and crewmember duties; structures, which will document airframe wreckage and the accident scene; power plants, which will focus on aircraft engines and engine accessories; systems, which will study the electrical, hydraulic and pneumatic components of the two aircraft; air traffic control, which will review flight track surveillance information, including radar, and controller-pilot communications; survival factors, which will analyze the injuries to the crew and passengers and crash and rescue efforts; and a helicopter group.

The investigation also will include a human-performance group that will be a part of the operations, air traffic control and helicopter groups and will study the crew performance and any factors that could be involved such as human error, including fatigue, medications, medical histories, training and workload, Inman said.

How long will the investigation take?

NTSB officials did not say Thursday how long the investigation would take, but accident investigations often take between one to two years to complete.

The agency typically releases a preliminary report within a few weeks of the accident that includes a synopsis of information collected at the scene.

What is the NTSB’s history?

The NTSB history dates to 1926, when Congress passed a law charging the U.S. Department of Commerce with investigating aircraft accidents.

It was established as an independent agency within the U.S. Department of Transportation in 1967 and then separated by Congress in 1974 as a stand-alone organization, fully independent from any other federal agencies.

Since its creation in 1967, the agency reports it has investigated more than 153,000 aviation accidents and incidents.