This was despite a Qatar Airways booking that saw her only transiting through Doha, with a few hours in the airport before her connecting flight to Paris.
International transit stops are meant to be simple and straightforward. You leave one flight, pass through security checks, grab a coffee or a juice, have a shower if it's available and wander through the terminal to your boarding gate. But they don't always play out so smoothly. Even though you're not actually entering the country you're transiting through, where you've come from, how long you're staying and who you're with can turn your transit stop into a flightmare.
If you're travelling on a split ticket, booking your first flight sector with one airline with a separate booking for a connecting flight aboard another airline, you might have to retrieve your checked baggage off the first flight and check in for the second. If that happens in a foreign country you'll need to pass through immigration, and that could require a visa, or a visa waiver if you're eligible.
Without it you won't be permitted to proceed to the baggage collection area, or go to the check-in desks. You could end up being sent back to wherever you came from, or having to pay an exorbitant amount to resolve the situation.
This problem could also occur if your transfer involves airlines that do not have an interline agreement, a relationship allowing baggage transfers between them without your involvement. If you book a ticket through an online travel agent, it's not uncommon for them to issue tickets for different airlines that do not have such an agreement. Traveller has recently received letters from readers who ran into this problem when trying to transit through Vietnam without a visa.