The US Capitol building is seen in Washington, DC Nov 10, 2022. The balance of power in the next US Congress is still undecided as of late Thursday night, two days after the 2022 midterm elections. Photo:Xinhua

 US federal safety officials will launch an investigation into a Hawaiian Airlines flight after severe turbulence injured 36 people aboard, while five people were hospitalized in Houston on Monday after a second flight was rocked by turbulence en route from Brazil.

There was no indication that the two instances of turbulence were related. Air travel is exceptionally busy around the world due to the winter holidays.

The Hawaiian Airlines flight departed Phoenix and was nearing Honolulu around 10:35 am HST (2035 GMT) on Sunday when it hit the turbulence, according to the statement of the US Federal Aviation Administration (FAA).

Hawaiian Airlines said in a statement on Monday that 36 people had been evaluated at the airport upon landing, and that it was "continuing to support" the 17 passengers and three crew members who were transported to area hospitals for treatment, 11 with serious injuries.

Meanwhile, two passengers and three crew members on a United Airlines flight from Rio de Janeiro were injured early on Monday by turbulence en route to Houston, Texas.

An ABC News affiliate captured video of ambulances responding to Bush Intercontinental Airport when the United Airlines flight landed around 5:30 am CST (1130 GMT). It reported that the flight hit turbulence while passing over Cancun, Mexico. Of the 20 people hospitalized after the Hawaiian Airlines flight, 11 were brought to emergency rooms in serious condition, according to Honolulu Emergency Medical Services.

Injuries included head laceration, bruises, and loss of consciousness, the EMS said in a statement. A spokesperson said they had no further updates to provide.

Hawaiian Airlines said in its statement on Monday that it was conducting a thorough inspection of the Airbus A330 aircraft before returning it to service.

In video of the inside of the plane shown on CNN, debris was scattered on the floor and there were multiple cracks in the ceiling where people or objects apparently hit with force.

The airline declined to comment beyond the statement, citing the impending safety board investigation.

Reuters