Bram

One structural point that changes how you should pack regardless of how the conversation goes.

Even with the best preparation, there will be a flight where the aircraft is small and the bag genuinely cannot come aboard. So the goal should not be "this bag never leaves me" — it should be "nothing irreplaceable is ever in a bag that could leave me".

In practice that means a second, smaller pouch that is unambiguously personal-item sized and holds the medication itself plus anything you would need in the next day. That pouch never gets checked because it fits under a seat on any aircraft flying. The larger bag can then hold the bulkier equipment and you can afford to lose the argument about it.

Splitting the risk is more reliable than winning every negotiation, and it means the one time you meet an inflexible crew member is not the time it matters.

There is a specific historical fork rather than mere inertia.

Most of the world's pictogram signage descends from an international convention on road signs and signals agreed in the 1960s, which standardised shapes, colours and symbols across signatory countries. That is why a European driver can cross six borders and read every sign without knowing a word of the local language.

The United States never adopted it. It has its own national manual instead, which predates the convention in spirit and evolved separately, and Canada, Australia and a few others follow the American approach more closely than the European one despite geography suggesting otherwise.

So the two systems are not one standard applied loosely; they are two standards that were already established before anyone tried to merge them, and by then every road in both blocs was already signed.

On who receives what, in broad strokes — details vary a lot by country and by route, so treat this as the shape rather than the specifics.

• The departure state generally has access, since the flight originates under its authority.
• The destination state commonly requires passenger data to be transmitted in advance of arrival, which is why check-in for some destinations demands full passport details rather than just a name. That is the whole point of collecting them at booking.
• Transit states, where you land and change planes, typically receive data as well, because you are entering their airport.
• Overflown states are the interesting case, and the general answer is no — flying through airspace without landing does not normally involve any passenger data being handed over. Air traffic control deals in aircraft, not passengers: callsign, type, route, altitude.

That last point is the one that surprises most people, because it feels like the plane must be announcing itself in detail. It is announcing itself, just not about you.

Two practical things follow from this that are worth knowing as a traveller.

If your name is spelled differently on your birth certificate, your tickets or a visa than in your passport, an official observation is one of the mechanisms that exists to reconcile it. Whether you can get one added depends entirely on the issuing authority, but it is worth asking about rather than assuming nothing can be done.

And if you ever do have something on that page, expect it to be looked at. Border officers are used to the page being blank, so text on it draws attention in a way the same information elsewhere would not.

There is an established approach, and the first thing to understand is that the default is nobody enters the country at all.

An aircraft on the ground with its passengers aboard has not, in immigration terms, admitted anyone. If the diversion is short — refuelling, waiting out weather, a medical case being taken off — the ordinary outcome is that everyone stays on the aircraft or in a sterile transit area, and the question of documents never formally arises.

That covers the large majority of diversions. Documents only become an issue when passengers have to be taken off and cannot be put back on within a reasonable time: a technical fault requiring a replacement aircraft, a crew running out of legal duty hours, an airport closing overnight.

The structural reasons are worth knowing, because they explain why this is unlikely to change quickly.

Building rules. Minimum room sizes, window and ventilation requirements, fire regulations and occupancy limits in many Western jurisdictions effectively outlaw a room the size of a capsule as a sleeping unit. Where capsule-style places do exist, they are usually licensed as hostels rather than hotels, which comes with its own constraints.

Land economics. Capsules make sense where central land is extremely expensive and labour is expensive, so packing more paying guests into the same floor area pays for itself. In much of Europe and North America, the cost stack is different enough that a small private room often earns nearly as much per square metre with far less regulatory friction.

Cultural expectation. Capsules in Japan are ordinary and unremarkable. Elsewhere the same product reads as either novelty or deprivation, which limits what it can charge.

Speaking generally rather than about your specific case, since the rules and their application differ by country and only the relevant authority can tell you where you stand.

The pattern people report is that a short overstay with a documented, involuntary cause is usually treated as an administrative matter rather than a serious one. The two things that consistently make the difference:

• Documentation. Keep everything the airline gave you — the rebooking, the hotel voucher, the delay notice, the original ticket showing the intended departure date. This is the entire evidentiary basis for "involuntary", and it is far easier to keep it than to obtain it later.
• Disclosure. Raising it yourself at departure control is generally better received than having it discovered. It is going to be seen either way, because exit is where the dates get compared.

Expect it to be recorded in some form even if nothing further happens. A recorded, explained overstay is a very different thing from an unexplained one on a future application.

Germany and central Europe are the strongest region for the commercial version, because the medieval-tavern format there has been running long enough that some places genuinely researched it rather than costumed it.

The filter I use when reading a menu, which separates the two categories quickly:

• Does it name sources? Places doing real reconstruction tend to say which manuscript or period cookbook a dish comes from, because that is the interesting part to them.
• Are the spices right? Medieval European cooking of the wealthy used a lot of what we now think of as sweet spice on savoury food, plus verjuice or vinegar for sourness. A menu with tomatoes, potatoes, chillies or chocolate is not period, since all of those arrived from the Americas later.
• Is the sweetness in the wrong place? Sugar was a spice, not a dessert category. A meal that ends with a modern pudding has usually not thought about it.

That last one is the single fastest test.