The incident occured on a flight from Oakland International Airport (OAK) to Santa Ana’s John Wayne Orange County Airport (SNA) on 1 July.
The National Transportation Safety Board (NTSB) said the impact of the landing was so hard that the flight attendant thought the plane had crashed.
According to their report, she felt a pain in her back and neck and was unable to move, and had to be taken to hospital where she was diagnosed with a compression fracture to a vertebrae in her upper back.
A report from the investigation into the incident was released last week by the NTSB.
It states that: “According to the flight crew, they were flying a visual approach to runway 20R at SNA.
“They were aiming for the touchdown zone due to its short runway and trying to fly the aircraft onto the runway with minimal floating.
“However, it ended up being a firm landing. Shortly after exiting the runway, the flight crew were informed that the “B” position flight attendant seated in the aft jump seat had injured her back on landing and required medical assistance.”
The NTSB completed its investigation without saying what caused the hard landing.
The safety board also said none of the other 141 passengers and crew members on board were injured in the incident.
The NTSB, which did not travel to the accident site, has not made its documents from the investigation publicly available.
John Wayne Airport has the shortest runway of any major airport in the US, measuring only 5,700 feet long (1,700 metres). In comparison, runways at nearby Los Angeles International Airport range between 8,900 and nearly 13,000 feet (2,700 to 3,900 metres).
The Independent has approached Southwest Airlines for comment.