Why are airplanes always white?

A lot (not all) of them are white because it reflects the sun's rays and keeps things cooler inside while the plane is on the ground. At the same time the paint is a major player in corrosion protection for the aluminum skin.
Except for a few hot spots around the engine, the exterior of a plane is NOT stainless steel. The reflective finish seen on umpainted planes is a thin layer of pure aluminum applied to the surface of the aluminum sheet used for the skin itself. This type of sheet is callled alclad aluminum and has a high resistance to corrosion even when unpainted.

They aren't.
Some airlines (like American Airlines) leaves the aluminum skin polished, with just the markings and a red/white/blue strip down the cusp line
Different airlines have their own color scheme (called LIVERY).
Jon A is full of crap. the outer skin is a material called ALCLAD, which is a sheet of aluminum with a highly polished layer laminated to it, not stainless.
Also, no paint would show problems with the skin better than any paint hiding defects.

So people can say their plane is alwite.

They are not stainless steel, they're aluminum. More recently, composites like fiber glass and carbon fiber are also used. They are white because its the cheapest paint available and stands out against the sky fairly well. Southwest flys tan and orange 737s...

Hey, airplanes aren't always white. How many jetliners from different airlines or military aircraft have you seen in your life?

Here's an airliner that is very colorful..it's a Qantas jet named 'Wunala Dreaming'
and some airlines have 'theme' jets..like All Nippon's POKEMON 747-400 and Frontier Airlines' 'wild animal' themes.

airlines can get their planes with a graphic or colourful pics. but they wont bcoz they want to save their money.. save cost maa...

As has been adequately noted, airplanes are not always white. Most modern airplanes are primarily aluminum (NOT stainless steel, which is far too heavy for aircraft construction, except for some small areas, such as firewalls, exhaust areas, etc.), with a layer of alclad to protect the aluminum from rapid corrosion. Most airplanes are painted to minimize potential for corrosion. There are three reasons that white is commonly (though not always) used as the major base color for painted aircraft: 1) it is the least expensive paint color available (by comparison, red paint is far more costly, as the cost of the pigments is much higher); 2) white is one of the better colors for visibility, aiding in visual identification and separation between aircraft, and; 3) it is the most reflective of all the colors as to heat, which aids in keeping avionics cool and extending their life, especially when sitting on the ground in hot climates.

Planes aren't white unless you paint them white. Most airlines paint their planes white (called a eurowhite livery) for fuel savings. It seems to be the latest trend with most airlines. Some are more silver or polished, like American and Northwest (NWA is NOT polished), or painted with a different base color, like Southwest and Korean Air. Without paint, planes are silver/green/yellow.

commercial Airplanes are always white.

Southwest - brown

United Airlines - Grey

AA - silver

I`m not sure...i`m just thinking....The plane has been invented somewhere around the World War I. they used the planes in battles....so a white plane would have been a little more difficult to see, despite a red one. so the tradition stands... anyway this is stupid ... the truth may be about the sun and heat as some dudes answered above. anyway... flying is so sweet that you won`t look at your baby`s color.:D

So you can find them in the dark.

not all planes are white some are blue (southwest ) have u never seen the shamu 757 some leave then polished aluminum

white because reflects the rays of the sun and keeps the airplane cool.. and because white is a clean color doesnt show dirt that much and because its probably cheap :P

some are blue

Because who would want a purple one?

They aren't. They are stainless steel. Airlines then paint them according to their preferences...

Lighter colors make it easier to spot problems with the airplane's skin.