Inside the secret spaces on planes where passengers are banned

The next time you take to the skies, keep your eyes peeling for the secret compartments hidden away on planes. 

These cabins, known as 'crew rest compartments', are where pilots and flight attendants can get some much-needed downtime on long-haul flights, CNN Travel reported. But they are strictly off limits to passengers. 

'It's a little bit like Disney - we keep the magic behind closed doors,' United Airlines flight attendant Susannah Carr told the outlet. 

On newer aircraft such as the Boeing 787 and Airbus A350 these compartments are typically located above the main cabin in the upper fuselage. 

Some passengers may mistake the entrance for a restroom door or storage space, but behind is a secret ladder leading up to these little-known hidey holes.

Pictured: The crew rest area on a Boeing 777 passenger jet, located in the fuselage above the main cabin

The interior of the crew sleeping quarters on the Boeing 787 Dreamliner is seen during a media tour on February 12, 2012 in Singapore

Carr, who has worked on numerous Boeing aircraft, including the 787, 777 and 767, shared her insider's perspective on what crew rest compartments are really like with CNN Travel earlier this week.

There are usually two sets of rest quarters. 

One is for the pilots - complete with two bunks and a recliner seat - that sits above the cockpit. 

The cabin crew then have access to a second space with bunks that is typically located above the back galley where food and drinks are wheeled out from.

On older planes these compartments may be in the cargo hold or just a curtained-off section in the main cabin. 

'They can be quite comfortable,' Carr told CNN Travel. 

'They have a padded mattress, an air vent to keep the air circulating and temperature controls so you can keep it cooler or warmer, and we're provided with linens, usually similar to the ones used in business class on our international flights,' she said.

'I like them – but I'm also only about 5 foot 8 inches, so if you put a 6 foot 4 inch person in there, they might be a little tight.'

The Federal Aviation Administration regulates these sleeping quarters, imposing a litany of requirements on carriers, according to an agency advisory circular from 1994.

For instance, the dimensions of each bed needs to be at least 78 inches long and 30 inches wide. That's a fair bit thinner than a standard mattress, but about as long as a full XL.

The FAA also mandates that 'flight crew sleeping quarters should be in a location where intrusive noise, odors, and vibration have minimum affect on sleep.'

A crew rest area on an Emirates Airlines-operated plane, featuring wide beds and privacy curtains

A Lufthansa cabin crew member stands in the rest and sleeping area for the cabin crew of an Airbus A350-900

A viral video on TikTok posted by a flight attendant in February showed off the crew's sleeping quarters on a luxury Emirates Airlines plane. 

He opens an innocuous-looking door that looks like it leads to a bathroom but in fact reveals a spiral staircase that leads up to what some describe as a 'hotel hallway'.

Inside there are at least eight curtained-off beds, some of which have televisions alongside.

Many viewers claimed the space was better than business or even first class. 

'Can I pay my flight [attendant] to rent it out lol,' one commented.

Others made 'mile high club' jokes, while some claimed the cozy beds made them want to become flight attendants themselves.

The sleeping quarters for Emirates flight attendants, complete with eight beds flanking the hallway

Despite most cabin crews not getting access to in-flight entertainment, Emirates flight attendants get TVs above their beds

But not every aircraft is as swanky as Emirates. 

On older planes, such as the Boeing 767, the rest areas are located in the main cabin, and are just recliner seats with curtains around them.

'They are very heavy curtains, they block out light and a good amount of sound, but not if you've got an energetic crowd on the plane or an upset child. We've had passengers open the curtains, looking for something or thinking they'd be going into the galley, so it's not necessarily the best rest,' Carr told CNN Travel.

United Airlines has the oldest fleet of aircraft with an average age of 16.3 years, while an Emirates plane has an average age of 10.3 years, according to data from airfleets.net. 

The rest areas are not used on every flight, particularly if it is a short domestic trip.

But on long haul flights, cabin crew members usually spend at least 10 percent of their time hidden away from the passengers.

'On average, I would say that means about 1.5 hours per long-haul flight,' Karoliina Åman, a flight attendant with Finnair who works on Airbus A330 and A350 aircraft, told CNN Travel. 

'Since we don't have any private area in the aircraft for our lunch or coffee breaks, this rest period is extremely important and helpful for us,' she added.

The crew rest area on a Boeing 787 Dreamliner departing to Houston at Denver International Airport in Denver, Colorado

A small staircase leads to a compartment of sleeping berths for long haul crew members on the 787 Dreamliner

She continued: 'This is the moment during the flight when we don't answer passengers' calls or do any other task but rest, and let our feet and mind have their break too. The purpose of this rest is to maintain an alert and ready mindset during the whole flight so that if anything unexpected happens, we are ready to take action.'

There is also a hierarchy within flight crews, with senior employees getting more flexibility over when they get to rest. 

'Everything in our industry is seniority based, from the schedule you fly to the routes you can hold, to your days off,' Carr explained to CNN. 

'The longer you've been there, the better the perks and one of those perks is picking your crew break time – we go on seniority order, so the person who's the most senior on the flight gets to choose whether they prefer the first break or the second break.'

The pilots also need their rest, and their compartments are usually near the cockpit. 

Depending on how long the flight is, there can be up to four pilots on board, but there always has to be two pilots in the cockpit operating the aircraft.

This means their rest area usually only has two bunks and sometimes a seat with in-flight entertainment - which the cabin crew don't get.

The pilots' rest area usually only has two bunks and sometimes there's a seat with in-flight entertainment, something the cabin crew doesn't get. 

Aleksi Kuosmanen, deputy fleet chief pilot at Finnair, said he likes the resting area on the Airbus A350, which is above the forward galley.

'It has really good curtains, you can adjust the temperature really well, there's great ventilation,' he said, adding, 'You don't hear anything of what's happening in the galleys, it's really quiet and comfortable.'

So next time you're on board, keep your eyes peeled. But beware that most flight attendants try to keep these areas well hidden.

'You don't necessarily want to know that your flight attendants are getting a little bit of shuteye, but at the same time you'll be happy when we pop up after our little cat nap all fresh as a daisy,' Carr said.