The kind of travellers who have their travel clothes packed and know what music to play during take-off, and who have nothing whatsoever when their stomach reaches the age of 30, 30 minutes after the in flight meal. That's now a topic of discussion among travel-health experts and pharmacists with the same downbeat answer: It's the things that no one blogs about that are the ones to pack.

There is a very dull list that keeps on going round among the registered pharmacists who specialise in travel medicine. Oral rehydration salts. A broad-spectrum antidiarrhoeal. Anti-Allergic Medications for Altitude allergies. Paracetamol or ibuprofen. Motion-sickness tablets. A blister plaster or two, adhesive dressings and sufficient amount of any prescription medication to cover any delays (plus a copy of the prescription). It's not anything that photographs well. Everything that's used is all of it.

There's more to it than fashion: the reason the advice is starting to pick up is due to arithmetic. More people are flying for longer than ever in commercial aviation. Estimates of industry passenger numbers worldwide vary from 2.75 billion to nearly 5 billion passengers per year, depending on the year and source, and a significant percentage of those travellers are now on an ultra long-haul journey that exceeds sixteen, and in some years eighteen, hours of flight. The longer they remain in the air, the longer they suffer from being exposed to changes in cabin pressures, dehydration, low humidity and reduced mobility all of which can make a health problem in-cabin.

The statistics of how often that occurs is more solid than what most people think. A large multi-airline study, published in the JAMA Network Open, on over 77,000 in-flight medical emergencies over 84 airlines and approximately 3.1 billion passenger boardings revealed that a medical emergency happens on an average of one in every 212 boardings. About 8 percent of those affected passengers required hospitalization upon landing and nearly 2 percent of the occurrences necessitated a diversion (most often suspected strokes, seizures, chest pain, and sudden alteration in mental status). In a recent review of nearly 12,000 in-flight medical emergencies, researchers found that almost two-thirds of cases involved faints, difficulty breathing or gastrointestinal symptoms and a doctor passenger was present to assist almost half the time. None of these are uncommon situations. They are the type that can be flattened or cut with a simple kit and a bit of work.

The economics are also very sharp at diversions. An average unplanned medical diversion has been cited anywhere from $15,000 to nearly $900,000 depending on the type of aircraft and the distance it had to back track and the route. That cost structure is quietly borne by airlines, insurers, and ground support, and it's what has spurred an increase in satellite linked telemedicine on board over the last few years it's a more cost-effective, efficient means to determine if a passenger really needs to change runways or just a seat recliner and an antacid.

The demand side of the same has become a true market. The analysts monitoring the travel health kit market estimate that the global market size at $3.4 billion in 2024 should more than double to $7.8 billion by 2033. A related but distinct category is travel vaccination, which is projected to approach nearly $8.7 billion this year, and continue to increase at nearly 10 percent per year over the next decade, largely due to increased global travel and new travel corridors with increased immunisation requirements. The value of other travel paraphernalia such as water bottles, bag organizers and yes, first aid pouches that often accompany passport holders on packing lists is estimated at $2.46 billion, and Asia-Pacific alone is responsible for nearly half of that spending. Even the decidedly non-glamorous first-aid kit category is on the rise, and will nearly double in value by the mid-2030s with the tightening of workplace and household preparedness rules worldwide.

There is also a more muted economic undercurrent going on. Insurers whose business is travel insurance have a stake in a lesser number of claims, and a passenger who travels with a modest kit and an understanding of what their policy covers is a cheaper passenger whose insurance can be sold. Which is why the travel insurance industry has focused so strongly on preventative messaging in recent years policy sales and packing lists, destination health information and warnings to include an original prescription for medication, and a match for most countries that allow a 30- to 90-day personal supply, but not beyond.

This is important, especially for Indian travellers. International prescription regulations differ widely by country and brand names that are well known in your home country may not be available to fill at the pharmacy, and a chronic medical condition that you can easily handle at home can turn into a problem on the road if you don't have the proper paperwork. The recommendations that came from health professionals in both the health industry and aviation health research are all basically the same: pack for the normal emergency, never for the movie emergency. It's not often a heart attack at 35,000 feet that spoils a trip. It's dehydration, a stomach bug or a headache nobody thought to bring along.