(CNN) — Few people enjoy in-flight turbulence, but while it's anxiety-inducing you're usually pretty safe and secure with your seat belt fastened.
But on a Thomas Cook flight from Varadero Airport, Cuba, to Manchester Airport in the UK earlier this year, sudden unexpected severe turbulence caused two cabin crew members to suffer injuries -- with one flight attendant breaking an ankle and the other receiving bruising to their back and shoulders.
A recently released UK Air Accidents Investigation Branch report revealed that turbulence lasting just 90 seconds resulted in this crew member's foot and ankle getting trapped underneath a catering cart.
"Their foot remained wedged until the turbulence subsided sufficiently to allow other crew members to help free them," reads the report.
The incident took place mid-Atlantic in August 2019, while the plane was cruising at 37,000 feet. The turbulence resulted in a 500-foot altitude gain and autopilot disconnection.
Once it ended, autopilot reconnected and the flight carried on the journey to Manchester, where the injured crew member went to hospital upon arrival.
The aircraft, an Airbus A330-243, received minor surface damage.
The turbulence was caused by a cumulonimbus cloud.
KAREN BLEIER/AFP via Getty Images
The Air Accidents Investigation Branch Report concluded there could have been further injuries had the seat belt signs not been turned on during the incident.
The signs had been illuminated just five minutes earlier, as a precaution in case of possible light turbulence. There were 320 passengers on board and 11 crew members.
At the start of the flight, during the ascent from Varadero, the flight crew became aware the aircraft's weather radar displays weren't highlighting "several significant thunderstorms" in the flight's vicinity.
They changed the weather radar selection, which, the report says "appeared to solve the problem."
Still, the actual incident was a surprise -- the flight crew were "aware of the risks associated with CB clouds" [cumulonimbus clouds AKA dense, vertical clouds], but they were trying to avoid them.
"The onset of severe turbulence was rapid and unexpected," the report says.
An announcement was made for cabin crew to immediately take to their seats, but less than five seconds later, the plane was being walloped.
For the next hour of the flight, there was still "light to moderate turbulence" -- although nowhere near as bad as before. During that time, the weather radar system being used failed, and the "degraded" original weather monitoring system was used for the rest of the flight.
If someone falls ill or gets seriously injured on a flight, air crew can make the decision to divert the flight -- although that's usually avoided if possible, due to the cost and inconvenience.
In this incidence, the commander consulted with Medlink -- the in-flight medical advisory service -- and decided to continue the flight to Manchester as planned.
While there have been past alarming reports of crew and passengers injured during turbulence, specialist travel doctor Richard Dawood tells CNN Travel that turbulence-related injuries are very rare.
"Turbulence is scary -- even if you're an experienced traveler," says Dawood "It can get to a point where it really can be quite disturbing and destabilizing, literally."
But more often than not, it only lasts for a short amount of time, says the doctor, and flight crew will always try their best to avoid.
"Documented injuries from this are incredibly rare, we don't often hear of people who've really damaged themselves."
It's a good reason to keep your seat buckled, he says.
"That should be the standard and most airlines tell you that in their announcements," adds Dawood. "Certainly on an overnight flight, if you're able to go sleep you should keep your seat belt visible at all times. It's a really good thing to be doing, because it can be very unexpected."