Thirty-six people on a Hawaiian Airlines flight required medical treatment and 11 were seriously injured Sunday as part of a “mass casualty emergency” caused by weather-related turbulence.

Hawaiian Airlines spokesperson Alex Da Silva said the incident occurred 30 minutes before landing on Hawaiian Airlines Flight 35, which was bound for Honolulu from Phoenix and encountered severe turbulence shortly before arrival at Daniel K. Inouye International Airport. Da Silva said the Airbus A330 aircraft, which was carrying a full load of 278 passengers and 10 crew members, landed safely in Honolulu at about 10:50 a.m.

Jim Ireland, director of the city Emergency Services Department, said a paramedic from American Medical Response and rescue firefighters from the state were the initial responders because they are based at the airport. Ireland said EMS was called at about 11:06 a.m. Sunday to provide backup. He said seven more AMR ambulances and an ambulance from the city and county responded.

Ireland said paramedics and emergency medical technicians transported 20 patients, from adults to 14 months old, to emergency rooms at Pali Momi, Straub and The Queen’s Medical Center.

Ireland said an initial triage report mentioned critical injuries at the scene, but once the patients were reevaluated 11 were found to have serious injuries and nine had minor injuries. Ireland said injuries ranged from head injuries to lacerations, bruising, loss of consciousness and nausea.

“We are also very happy and we feel fortunate that there were not any deaths or other critical injuries, and we are also very hopeful that they all will recover,” he said. “It was a team response today. I felt all the providers worked well together.”

Da Silva said Hawaiian Airlines is continuing to support the 17 passengers and three crew members who sustained injuries.

“We apologize to our guests for this incident and thank our crewmembers, first responders, hospital personnel, and airport teams for their coordinated response,” he said in a statement. “Hawaiian is conducting a thorough inspection of the aircraft before returning it to service.”

During a news conference Sunday afternoon, Hawaiian Airlines Chief Operating Officer Jon Snook said the aircraft suffered some internal damage, including panels that were bent and buckled and will need replacing.

“It’s going to require some maintenance work before we put it back in the air — mainly internal components in the cabin,” Snook said.

Hawaiian is cooperating with the National Transportation Safety Board, which will investigate the incident.

Snook said such incidents are “relatively uncommon.”

“We haven’t experienced an incident of this nature in our recent history, for sure,” he said.

Snook did not have a timeline for the NTSB investigation, but said that it will provide more information about factors that could have contributed to the incident, including the use of seat belts.

Snook said Hawaiian was “very familiar with the current weather forecast — there’s a lot of unstable air in the area.”

He said Hawaiian opted to divert three other flights bound for Maui to Oahu on Sunday due to low visibility. One of the flights was interisland, and two were trans-Pacific flights, Snook said.

In the case of Hawaiian Airlines Flight 35, he said that “there was no warning of this particular patch of air at that altitude was in any way dangerous — it caught everyone by surprise, which is often the case.

“There was a similar incident five yeas ago with Air Canada that had a very similar situation where you just don’t know it’s coming.”

An Air Canada flight was diverted to Hawaii after experiencing severe turbulence on July 11, 2019. As many as 37 passengers and flight crew on the flight, which had left Vancouver, British Columbia, and was bound for Sydney, reportedly experienced injuries. More than two dozen people were taken to the hospital.

Snook said he did not know how much altitude was lost during Sunday’s incident, which occurred around 36,000 feet. He said the flight recorder, which will be part of the NTSB investigation, should provide that information. He said the investigation also will include interviews with crew members.

Snook said the seat beat sign was on at the time the incident occurred, but he did not yet know how many people on board were wearing seat belts.

“We monitor the weather very carefully, and whenever there’s possibilities of turbulence, we’ll put on a seat belt sign and ask people to buckle up,” he said. “I would always recommend that people stay buckled whether the seat belt sign is on or not because sometimes these air pockets occur with no warning whatsoever.”

Snook said failing to wear a seat belt increases the risk of injuries because “if you don’t have your seat belt on, you stay where you are as the aircraft goes down.”

He added, “We know that some of the individuals who were injured didn’t have seat belts on.”

According to information on the Federal Aviation Administration’s website, “in nonfatal accidents, in-flight turbulence is the leading cause of injuries to airline passengers and flight attendants.”

That’s why FAA regulations require passengers to be seated with their seat belts fastened when airplanes are leaving the gate or climbing after takeoff, while landing and taxiing, and whenever seat belt signs are illuminated.

The FAA estimated in August that annually, 58 people in the United States are injured by turbulence while not wearing their seat belts.

According to FAA statistics, from 1980 through 2008 there were 234 turbulence accidents among U.S. air carriers, resulting in 298 serious injuries and three fatalities. Of those serious injuries, 184 of them involved flight attendants, and 114 involved passengers. Flight attendants are more prone to injury as they are often on their feet working during flights.

The FAA said that in at least two of the three turbulence-related fatalities, the passengers were not wearing their seat belts even though the seat belt sign was on.

Roughly two-thirds of turbulence-related accidents occur at or above 30,000 feet, the FAA said.