When Delta Air Lines bought Northwest Airlines for $2.6 billion last year, it inherited a hodgepodge of 436 planes that included everything from Airbus A330s to Boeing 747s and even some ancient DC-9s. Every one of them flies the Northwest colors, which means Delta has a whole lot of painting to do.

Painting all those planes is a Herculean task that will take the better part of two years and 40,000 gallons of paint. Slapping new colors on the fleet may seem trivial given everything else the airline has on its plate, but it's a top priority because few things do so much to rebuild the brand and appeal to customers. Delta has to combine Northwest's operations with its own and create a single consistent brand, and giving its planes a uniform look is one way to accomplish that.

The makeover started with the 16 Boeing 747-400s that Delta picked up in the Northwest deal, and it is noteworthy because Delta will be among the few domestic airlines flying the jumbo jets. Repainting the plane took 12 days, but time-lapse video cuts it down to three minutes and change.

Painting the plane required turning Delta's hangar at Southern California Logistics

Airport into a giant paint booth. The airline plans to paint 200 planes this year and finish the rest of them in 2010.

It's time-consuming but essential work because an airplane's livery is a highly visible manifestation of its brand. When Gordon Bethune took the reins at Continental Airlines in 1994, the company was just weeks away from insolvency but he had the fleet repainted. He believed planes that look like crap send the message that the airline is crap.

There also are practical reasons for repainting planes. When Tempe-based America West Airlines bought US Airways, for example, it ditched that airline's handsome blue paint scheme in favor of a lighter palette so its planes wouldn't get so hot in the Arizona heat.

Airbus says a decent paint job requires as many as six coats of paint, each requiring as long as 12 hours. All that paint weighs more than you might think. Doing the job right means laying on as many as 90 gallons of paint, according to the the blog Ask Captain Lim, and it adds between 330 and 550 pounds to the weight of the plane.

More weight means more fuel is burned, which is why some airlines forsake paint altogether. During the 1970s and 80s, financial basket case Eastern Airlines stripped the paint from its planes, opting instead for a brushed aluminum finish. American Airlines, which also flies planes that are largely unpainted, is going a step further, testing decals that would replace paint to save even more weight.

With airlines desperate to save cash, every pound counts.

Photo: Delta Air Lines. Yes, that's a Boeing 777-200LR in the photo, but it's the same livery used on the 747. Delta has not provided any photos of its 747s.

Original paint job for Qantas' first Airbus A380.

British Airways 757 repainted in livery for its Open Skies subsidiary.

Painting an Air New Zealand jet.