For two decades, Joseph D. Emerson had a successful career as an airline pilot.
After joining the Alaska Air Group in 2001 as a first officer, before becoming a pilot.
But, on Sunday, something suddenly chanegd when the pilot was involved in an incident that has shocked people who know him to the core.
While travelling in the flight deck jump seat in the cockpit of a plane flying from Seattle to San Francisco, the 44-year-old allegedly attempted to cut off fuel to the engines.
No one was hurt in the incident, authorities said, but the FBI is now working with the Port of Portland police to investigate the incident.
Many questions remain unanswered as to what led Mr Emerson to allegedly attempt to crash the plane mid-flight.
Here’s what we know so far:
What happened on the flight?
Authorities said Mr Emerson, who was off-duty at the time, was traveling in the flight deck jump seat in the cockpit when he suddenly tried to shut down both of the plane’s engines by pulling the fire extinguisher handles.
The 44-year-old was then subdued by flight crew as the captain and first officer intervened to keep the engines running.
The flight, which was travelling from Seattle to San Francisco, was diverted to Portland, and all 80 passengers on board were able to board a new plane.
Passengers who were on board the plane told ABC News that they were not immediately alerted to what Alaska Airlines called the “security threat”, until a flight attendant told them over the speaker that there was “an emergency situation and the plane needed to land immediately”.
Once the plane landed, police boarded the aircraft and arrested Mr Emerson, escorting him off the plane handcuffed.
Aubrey Gavello, one of the passengers on the plane, told Laura Coates Live the suspect was calm and cooperative as he was escorted off the plane.