You’ve bought yourself a private jet. Perhaps it’s a small Gulfstream for you and your nearest and dearest, or maybe it’s a Boeing 737, which can fit around 200 passengers. Now, all you have to do is get the interior right. You call on your favourite designer, who shows up with some fabric swatches, a bathroom catalogue, some upmarket furniture samples and… And it doesn’t happen like this at all. Having the interior of your jet redesigned is nothing like having your home, or even your yacht, made over.

“Once you go beyond the surface, you need an industrial designer and an engineer,” explains Howard Guy, director of the UK-based consultancy Design Q. Everything that goes into a plane has to be certified as aviation-safe and meet a raft of standards. The fabric covering your seats needs to be flame retardant. The foam inside the seats needs to be flame retardant. The seats themselves have to be bolted down and able to survive a 16G impact (humans rarely survive much above 10G).

Unusual custom jet requests: Real Fireplaces. You can have a very nice fake fireplace, but you can’t have a real fireplace.

The certification process is exhaustive. If you want a particular brand of domestic hi-fi, that’s fine, but it too needs to be certified – and certification could cost 10 times the price of the stereo. Even the pictures on your walls have to be certified. “You couldn’t have your favorite Rembrandt on the wall because it wouldn’t be fireproof,” says Michael Wilson, a representative of London-based VIP Completions and author of Jet Interiors: The Ultimate Buyers Guide to Personalized Business, Head-of-State and Private Jet Completions. “You’d have to have a copy.”

As well as passing regulations such as those set by the Federal Aviation Administration (FAA), you need to remember that a jet is not a domestic environment. For starters, as Jean-Pierre Alfano, creative director at AirJet Designs in Toulouse, points out, it’s very confined: even if larger planes are similar in size to a small apartment, you cannot open the window. Moreover, the materials used need to be very durable. If you’re flying from Montreal to Las Vegas, you might go from -22°F to 104°F in a few hours, so you need materials such as wooden veneers that are far more resilient than those used at home.

“You can’t just go to any designer,” says Wilson. “A home designer or a yacht designer won’t always have an appreciation of what they can and cannot do.” So the approach tends to involve the client – or the client’s representatives – explaining what is wanted. The jet specialists will then make suggestions, schemes will be drawn up and CAD images produced. It may be possible for your favorite designer to have input, but they will be working with others and under tight constraints.

What is involved in a normal fit-out will depend on the size of the plane and the number of people it needs to accommodate (as every person must have a seat that is certified for takeoff and landing).

A standard fit-out might be something fairly modest: a bedroom, a bathroom, and a dining area. Mod cons could include live TV and Wi-Fi. Again, the cost in the air is several orders of magnitude higher than on the ground – an entertainment system that lets you watch TV live via satellite could come in at $750,000. There are also “invisible” luxuries such as soundproofing. Timothy O’Hara, design manager at Texas-based Aeria Luxury Interiors, says, “Everyone wants the ambient noise within their aircraft to be below 50 decibels (a commercial plane is typically 70-80). You can get down to 40, but soundproofing is heavy and can limit your plane’s range.”

So far, so pedestrian. Of course, if you’ve splashed out on your own jet, you’ll want it to be special, unique to you. Some level of bespokery is available from the manufacturers. The fractional aviation company NetJets gets the suppliers such as Bombardier to build in the majority of changes it wants. “Our interiors are customer-designed featuring specifically selected wood veneers, leathers, and fabrics based on research we do with our customers,” says senior vice president of communications Thomas Hoyt.

A complete redesign, however, is a very different matter – and the restrictions and engineering are reflected in the price. Wilson says that, while a Gulfstream might cost $5 million to deck out, a Boeing 737 could set you back from $30 million to $50 million. A really big jet might cost you $200 million. The thing to remember is that almost every job is unique – nearly everything will be a one-off.

As for the really eye-opening stuff, well, if you have the money, the luxury jet designers will try to make it happen. O’Hara says, “You do get people asking for bathtubs and hot tubs.” Here it comes down to logistics and engineering: a bathtub full of water is a very heavy object and can only positioned in certain areas of the plane. Then there’s the slopping of water; normally you have a spill lip to deal with this.

Other feats have included in-flight dance floors and even prayer rooms that are mounted on turntables so that the room faces Mecca wherever the plane is in the world. Wilson says that he’s currently working on the world’s first enclosed “waterfall” for a 787 Dreamliner. “It’s taken a lot of engineering and approval.”

As for what is not possible, Alfano says, “You do get requests for real fireplaces. You can have a very nice fake fireplace, but you cannot have a real fireplace.”