An overnight flight from Colombia to New York ended in hospital for several people on board after the aircraft ran into violent turbulence that the crew had no way to see coming.

Avianca Flight 42 was flying from Medellín to John F. Kennedy International Airport when it hit what the airline described as unexpected turbulence. The pilots diverted to Miami International Airport, landing safely at around 3:30am on Friday. Colombian carrier Avianca said three cabin crew members and six passengers were affected, while Miami-Dade Fire Rescue counted eight patients taken to hospital — one to the main trauma centre by fire crews, seven more by private ambulance. A nine-month-old was among those injured, according to early reports, though the full extent of the injuries has not been confirmed.

The response was large enough that the airport classified it as a Level 1 mass casualty event, a designation normally reserved for emergencies involving roughly three to ten patients that push local medical resources. Passenger video from the cabin showed people holding ice packs to their heads and being told to stay in their seats. An overhead locker reportedly sprang open during the rough patch, and other footage showed passengers on stretchers, one wearing a neck brace.

Another traveller waiting at the gate, Maria Paula Jimenez, told CBS Miami that five to seven ambulances were parked on the tarmac with their lights on as the plane came in. Avianca said its ground team helped the rest of the passengers continue on to New York, and the Federal Aviation Administration is now investigating.

Why does this matter to anyone booking a flight? Because clear-air turbulence — the kind that hits without warning, outside of storms and often without any radar indication — is exactly what happened here. Seatbelt signs were likely on or about to be, and the people hurt were most often those standing, in the galley, or unstrapped when the aircraft dropped. The practical takeaway is dull but real: keep your seatbelt fastened whenever you're seated, even when the cabin feels calm, and take extra care during crew service periods on long overnight sectors. Cabin crew are injured in turbulence incidents disproportionately often for precisely this reason.

The route involved is a busy one — Medellín to New York is a popular link for both Colombian travellers and the large diaspora — so this is unlikely to change day-to-day operations. But it's a fresh reminder, after a string of high-profile turbulence incidents in recent years, that injuries on board are far more common from being thrown around the cabin than from anything the aircraft itself does.