Photos: Severe turbulence on two flights leaves 41 injured; US safety board to investigate

US federal safety officials will launch an investigation into a Hawaiian Airlines flight after severe turbulence injured 36 people aboard, while five people were hospitalised 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 this week due to the winter holidays.

The Hawaiian Airlines flight departed Phoenix and was nearing Honolulu around 10.35am HST (20.35 GMT) on Sunday when it hit the turbulence, according to the US Federal Aviation Administration (FAA).

On Monday, the US National Transportation Safety Board announced it would investigate the incident.

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 crewmembers who were transported to area hospitals for treatment, of which 11 had serious injuries.

Meanwhile, two passengers and three crewmembers on a United Airlines flight from Rio de Janeiro were injured early on Monday by turbulence en route to Houston, Texas. Medical personnel brought them to a local hospital with "minor injuries", United Airlines said in a statement.

An ABC News affiliate captured video of ambulances responding to Bush Intercontinental Airport when the United Airlines flight landed around 5.30am CST (11.30 GMT). It reported that the flight hit turbulence while passing over Cancun, Mexico, citing air traffic radio scanners.

Of the 20 people hospitalised after the Hawaiian Airlines flight, 11 were brought to emergency rooms in a serious condition, according to the 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.

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