As the Year of the Pig in the Chinese zodiac gets underway, from an aviation perspective we are reminded of those ‘swine flew’ cases which have in the past hogged the headlines. Although you might think that pigs and passengers do not mix, pigs have on occasion been known to snuffle around the aircraft cabin.

One notable example was the 20-stone (130kg) pet pig which occupied three First Class seats on an American Airlines flight from Philadelphia to Seattle in 2000. Its owners had insisted upon the pig accompanying them on the flight, saying that it was a "therapeutic companion pet", and relied on a doctor’s note to that effect. Despite attempts to strap the pig in, it reportedly became restless after take-off and began sauntering through the First Class cabin. As the flight landed in Seattle the pig panicked, and at one point charged the cockpit door. Eventually it was lured from a hiding place in the galley with food, and had to be pushed off the aircraft by four cabin crew.

In a more recent example of porcine misbehaviour, in December 2014 a passenger who was accompanied by a large pig was asked to leave a US Airways flight after the pig became disruptive during boarding.

Both of these instances arose in the US, owing to specific US legislation (the US Air Carrier Access Act) which prohibits commercial airlines in the US from discriminating against passengers with disabilities. As a result, service animals and emotional support animals – animals that the passenger claims he or she needs due to an emotional or mental disability – must be allowed in the aircraft cabin, subject to certain exceptions. Accordingly, pigs have appeared on board aircraft, along with peacocks, ducks, turkeys, iguanas and other exotic species. However, passengers travelling with fake emotional support animals is apparently a growing problem, with some people now using this as cover to travel with their pets. Unsurprisingly, therefore, the US Department of Transportation is looking to tighten up its service animal rules.

Under the US legislation foreign airlines are not required to carry service animals other than dogs, although issues could conceivably arise where a passenger is travelling under a US airline’s code on a flight operated by a foreign code-share airline partner.

As far as Hong Kong is concerned, the Civil Aviation Department’s regulations only allow guide dogs and specially trained disability assistance dogs to travel in the aircraft cabin, subject to prior approval from the Agriculture, Fisheries and Conservation Department.

And so, to answer the question, yes pigs can (currently) fly in the passenger cabin – but not to Hong Kong.