The news that several budget airlines are set to introduce standing-only seat options rocked the world this week. 

The bike-style padded seats allow passengers to lean at an angle without completely sitting down – and could be introduced as early as 2026.

However, the standing-only seats aren't the only bizarre airplane seats to hit the headlines in recent months. 

In February, Airbus revealed that it was working with Spanish start-up, Chaise Longue, on a double-decker plane seat. 

The concept features one row of seats on a raised platform, followed by one row at a normal level, and so on. 

For passengers up top, worrying about the etiquette of reclining will be a thing of the past, with no one directly behind to complain about it.

Meanwhile, bottom passengers would be able to stretch their legs more and even put their legs up slightly, thanks to added space under the chair in front.

However, the idea proved controversial among social media users, with one posting: 'Last thing I want when flying is being stuck in someone's fart zone.'  

The dual level concept is courtesy of Alejandro Núñez Vicente, CEO and founder of Chaise Longue, who said his firm is exploring 'early stage concepts' with Airbus.

'After 4 exciting years pursuing my dream of improving the passenger experience and giving passengers what they truly deserve, today I am very excited to make [this] announcement,' Mr Vicente said in a LinkedIn post. 

'It's the dawn of a new era for commercial aviation, so I hope that you are as excited as we are with this announcement and that soon, you can be crossing the skies in a more comfortable, spacious and two-level seat.' 

The initial images have raised concerns among many travellers about people passing wind in the cabin. 

One person on X said: 'The nice thing about this arrangement, is that farts from the higher seats in front of you will hit you right in the mouth so you don't have to wonder where they came from.'

In response, Mr Vicente said: 'With some common sense and maturity you should be able to find your answer.'

He added: 'Gas in general doesn't go through solid objects like seat cushions, seat covers and plastic shells.' 

It's unclear when the two parties are aiming to roll the design out to aircraft; MailOnline has contacted them for more information. 

Mr Vicente, who studied industrial engineering at Brunel University of London, started building his first plane seat prototype by hand in 2021 using just a 'bunch of planks'. 

Chaise Longue has provided a digital model online of the layout, which lets web users control a Sim-like figure in a mock-up of an aircraft cabin. 

According to the concept – which has also piqued the interest of Emirates – passengers would decide whether they were booking top seats or bottom seats. 

From the promo images, it seems passengers in the bottom seats would have ample legroom – but less space behind them to recline. 

Conversely, the top passengers would have lots of room to stretch back but not quite as much legroom. 

However, considering the bottom passenger would have their head directly behind a fellow flyer's backside, the top seats may prove more popular. 

What's more, bottom passengers would have the back of someone's chair looming high over them, which could either increase the sense of privacy, or claustrophobia. 

Everyone would have space under their own seat to put their baggage – but the bottom row passengers would get a little extra space in front of them too. 

Notably, the design gets rid of the overhead luggage compartments in order to utilize the plane cabin's height as much as possible. 

Mr Vicente told CNN he's not on a mission to eradicate normal airplane seating.

Instead, he envisages a cabin where his concept is in the middle, flanked by two rows of traditional airplane seating, but he admitted 'there is still a long development ahead'. 

He also said he's thankful Airbus sees 'the true potential of two-level seating', while adding he's 'open for collaboration' with other aviation companies.

Airbus confirmed the collaboration but offered scant further details about the project.  

An Airbus spokesperson said: 'Chaise Longue is exploring some early stage concepts with Airbus on two-level seating solutions for Airbus commercial aircraft.'

'Given the nature of this early phase level,' the spokesperson added, Airbus preferred 'not to further comment at this stage'.