Exiting a plane after a long-haul flight is often like walking through a landfill site.

“The cabin of my 767 looks like a typhoon has blown through it,” says Patrick Smith, a US pilot and author of Cockpit Confidential. “There are newspapers, cups, cans, plastic wrappers of every conceivable color and size, candy, gum, cookies, apple cores, and even sullied diapers, thrown under seats or crammed into pockets.”

And that’s just the stuff the cabin crew hasn’t managed to collect. Elsewhere in the plane – stowed away out of sight from passengers – are bin bags bulging with detritus.

Ground staff clear rubbish of an United Airlines flight Credit: GETTY

According to the International Air Transport Association (IATA), airline passengers generated 5.2 million tonnes of waste in 2016, which is roughly equivalent to 43,000 Boeing 787 Dreamliners. That figure, it warns, will double within 15 years under a “business as usual” approach.

With few exceptions most of that waste ends up being incinerated or thrown into a very deep hole. Barely anything is recycled. And not all of it is waste, in the traditional sense of the word; amongst the used cutlery, crumpled newspapers and contaminated food packaging are leftover meals, unused blankets and unused headphones, which are typically treated as trash.

“It’s disgraceful,” said Matt Rance, CEO of MNH Sustainable Cabin Services, which produces reusable headphones and blankets for airlines such as Emirates, Qantas and Etihad.

According to Rance, who describes himself as a “womble”, reusable products can be used up to five or six times by the airline and are better quality than their disposable counterparts. They also cost less per unit and can generate good PR for the carrier, he adds. “It’s a no brainer.”

At the end of a flight, MNH will collect the items, take them away for servicing and send them back to the airline as new. Headphones and blankets that have reached the end of their life will, he claims, be recycled.

“There are all sorts of weird and wonderful uses for them,” he told Telegraph Travel. “We use headset sponges, for example, in equestrian centres, to line the floor and protect horses’ hooves.”

Old blankets, meanwhile, are sent to homeless or relief charities.

Rance concedes that it can be hard changing the procurement habits of airlines, but praises “progressive” carriers for coming onboard.

He also says his company has something of a “lonely existence” – he rues the lack of similar organisations competing in the same space.

Airline passengers generated an estimated 5.2 million tonnes of rubbish in 2016 Credit: GETTY

That’s not to say others aren’t trying to do their bit. OzHarvest, for example, recently started working with Brisbane Airport to help distribute uneaten plane meals to homeless people. And last year Gatwick Airport opened an on-site biomass plant, which converts waste into energy. The plant also contains a recycling facility.

So why are such initiatives not more widespread?

“Many countries have very strict regulations on food [or food-contaminated waste] being brought in,” explained IATA’s Chris Goater. “They take a precautionary approach and often it has to be dealt with very strictly.” In other words, buried or burnt.

“We’re trying to change views on that,” he said, “but it’s a slow process.”

Goater claims airlines are largely onboard with recycling, but are stymied by regulations, which differ from country to country.

Much of the rubbish ends up in one of these – but is there another way? Credit: GETTY

“You can’t have one set of rules for the outbound leg of a flight and another for the inbound leg, it just gets far too difficult for the staff to cope with,” he said. “So in the end it just gets thrown away.”

Cabin waste costs the aviation industry an estimated $500 million (£388m) annually, a figure that excluded the cost of transporting it between continents.

“It adds extra weight [to the plane], which results in extra fuel consumption,” explained Magdalena Golebiewska, group environment manager at TUI.

Golebiewska believes better waste management procedures on the ground could help address the growing rubbish problem and reduce costs. If more airports had facilities like Gatwick’s, for example, they could save the money and time it takes to send waste to landfill.

For that to work, claims Rance, you would need the already-overstretched cabin crew to help separate waste on board each aircraft.

“If you could separate at source then you’re going to have a lot less contamination,” he said. “And that means less waste.”

Meanwhile the mountain of rubbish grows ever higher.