The travails of a long-haul flight are quickly forgotten when you disembark the plane in an exotic corner of the world and brace yourself for two weeks in the sun.
So imagine what it feels like to spend 12 hours on a plane only to land at the same cold and miserable European airport from which you departed.
That was the situation that 268 passengers found themselves in after flying with KLM last week – and the circumstances are extremely bizarre.
Those on board Flight KL685, operated by the Dutch flag carrier, departed Amsterdam on Thursday afternoon. The flight was bound for Mexico City, but turned back six hours later as it was skirting the coast of eastern Canada. Around 12 hours after departure, the 747 once again touched down on the tarmac at Amsterdam Schiphol and passengers became reacquainted with the cold air of the Dutch city.
KLM blamed the ongoing eruption of Popocatepetl, a snow-capped volcano around a 90-minute drive from Mexico City, for the U-turn.
"The reason for the return was the unfavourable flying conditions above Mexico after activity of the volcano," the airline's social media account tweeted, adding that safety was the priority.
And while no one disputed that Popocatepetl had been emitting smoke and ash into the atmosphere – this was confirmed by the Volcanic Ash Advisory Center, which said on Thursday that plumes had risen to 24,000 feet (7,300m) – there was some debate as to whether it was enough to send a plane that had already reached the shores of New Brunswick all the way back to the Netherlands.
It also became apparent that scores of other aircraft continued to operate in and around Mexico over the timeframe. For example, Iberia's Thursday service from Madrid to Mexico City landed without incident.
It then emerged that the jumbo jet did not just have human passengers on board. The 747 was one of KLM's "Combi" planes, with space for 268 passengers as well as a "cargo transport deck". And on board this particular flight were as many as 28 horses.
Tom Podolec, an aviation journalist in Toronto, was told by KLM that the plane contained no such thing. "Please know that we don't transport horses," it said. But the airline retracted that statement shortly afterwards, and claimed that the reason for the return to Europe was indeed the equine cargo. "Landing at another airport was not possible because of the visa requirement for passengers and because there were also horses on board," KLM said.
Passengers criticised KLM for the disruption. Artur Fityka, who said he was on board Flight KL685, added: "Officially, we turned back because of volcanic ash. We could not land in any other airport in Mexico, USA or Canada due to 27/28 horses the plane had on board. Stuck at the airport without support."
There is an unfavourable flying conditions above Mexico after activity of the volcano Popocatepetl. Our apologies for the inconvenience. We will rebook the passengers on an alternative flight.
Another, Bruno Rijsman, tweeted: "KLM is not handling this well. No diversion to another airport in Mexico (because 'horses on board'). No hotel. No meal. No compensation. Trying to get some sleep on airport floor waiting for horrible multi-stopover rebooking."
KLM said passengers were cared for and rebooked onto another flight, with normal service resuming the next day.
The Dutch carrier makes no secret of its Combi planes, hosting a web page explaining how the 747-400 Combi is its biggest aircraft. "This type of Boeing transports all kinds of cargo: from small packages to large animals, like elephants or horses," it says. "We've been flying with this type of aircraft since 1989, so that's about 30 years."
The particular plane in question last week was PH-BFT, which has been with KLM for the duration of its service, since 1997.
KLM is, of course, not alone in having to turn planes around for peculiar reasons. In September it emerged that an aircraft with 337 passengers, bound for Cancun from Frankfurt, was diverted to Shannon, Ireland, after the pilot spilled coffee on a control panel.
Other aircraft have had plans altered by strong aromas emanating from the toilet, disruptive passengers, and swarms of bees.
The Telegraph, London