Fainting is the most common in-flight medical emergency, according to new research that detailed the number, type and frequency of medical emergencies on board two airlines.

Michael Sand led a team of researchers from the University of Bochum, Germany, and the University of California Los Angeles (UCLA), who analyzed 10,189 different emergencies.

He said, “Although in-flight medical emergencies are rare in general, they can have a significant effect on other passengers and crew, potentially with operational implications for the flight. The breakdown of the various medical emergencies encountered in our study showed that fainting was by far the most frequent medical condition, followed by stomach upsets, and heart conditions.”

In all, the authors found 5,307 cases of fainting (53.5%), 926 cases of gastrointestinal problems (8.9%) and 509 cases related to a cardiac condition (4.9%). The highly publicized problem of thrombosis accounted for a very small number of cases, although they do occur most often after a flight, rather than during.