(NEXSTAR) – The crew of a recent American Airlines flight was forced to make an immediate controlled descent following a “possible pressurization issue” on Thursday, dropping the plane’s altitude by nearly 20,000 feet in a span of minutes.

The plane ultimately landed safely at its intended destination in Gainesville, Florida, but not before causing concern among passengers, one of whom shared photos of himself and fellow travelers wearing the oxygen masks that fell from their overhead panels.

“I’ve flown a lot. This was scary,” wrote Harrison Hove, an education administrator and former anchor at Nexstar’s WCMH in Columbus, Ohio.

“Kudos to our amazing flight crew- cabin staff and pilots on @AmericanAir 5916,” Hove added. “The photos cannot capture the burning smell, loud bang or ear pops. Good to be on the ground.”

Both American Airlines and the Federal Aviation Administration said a “possible” pressurization issue was responsible incident, but could not yet say what may have caused any depressurization in the first place. The FAA is currently investigating.

The depressurization of an airline cabin, however, can be caused by several factors, according to the FAA. Skybrary, an online resource initiated in part by the United Nations’ International Civil Aviation Organization (ICAO) and the international Eurocontrol air-traffic management organization, says these events can be caused by structural failures, malfunctions concerning the plane’s pressurization system, or human actions (whether deliberate or inadvertent). More than one FAA document also refers to depressurization being the result of a “hole” or “opening” in the plane.

Depressurization events are often classified as “gradual,” “rapid” or “explosive” depending on how fast depressurization occurs. During this time, passengers may become aware of additional noise, wind, cooler temperatures, flying debris, fog, or expanding gas in their GI tract or ears, the FAA warns.

As passengers are often told, any change in cabin pressure will also result in the aircraft’s oxygen masks dropping from the overhead panels. These masks are required to supply at least a 10-minute supply of oxygen for all occupants of any plane flying over 25,000 feet, per FAA regulations.

Depending on the size of the plane, its altitude, and the rate of decompression (among other factors), the cockpit crew is then tasked with taking additional measures to keep passengers safe.

As was the case with the recent American Airlines incident, the cabin crew initiated a controlled decent — dropping from around 30,000 feet in altitude to just over 10,000 feet in less than 10 minutes, according to FlightAware — to bring the plane to an altitude where supplemental oxygen is not necessary, according to the FAA. (A representative for the FAA tells Nexstar commercial pilots are trained to descend to at least 12,000 feet, “below which supplemental oxygen is not required.”)

Such controlled descents are standard during depressurization incidents to prevent passengers from experiencing hypoxia, or a lack of oxygen to the lungs or blood. If hypoxia occurs, passengers may experience dizziness, lightheadedness, tingling, numbness, loss of consciousness, or, in cases where the plane remains at high altitude for too long without sufficient supplemental oxygen, possible permanent brain damage, the FAA says.

The effects of hypoxia are still possible even with supplemental oxygen, the FAA warns, though recovery from symptoms “usually occurs in a matter of seconds” once “100 percent oxygen is administered.” More severe cases may require medical attention, especially if symptoms persist.

No one was injured during last week’s American Airlines descent, the airline told Nexstar.

“While inflight, the crew received an indication of a possible pressurization issue and immediately and safely descended to a lower altitude,” reads a statement shared by the airline. “We apologize to our customers for any inconvenience and thank our team for their professionalism.”