In order to "brand" (see interview below) the current Northwest jets into Delta's colors, there'll be a fair amount of work involved. When Northwest last changed its logo, the new paintjobs were done on a staggered basis, as the jets went in for maintenance. There might still be "old" colors on some NWA jets, and that project started in 2003.
The airline can't ground its entire fleet for a paint job, so becoming branded will take time. How much? According to one expert on a forum:
I saw UAL 747-400's get painted in about 10-14 days working 3 shifts.... I've seen Piedmont Dash-8 get painted in about 7 days. Keep in mind a lot of that is driven by the number of people you have working the job. We did an E135.... not a Legacy... for a corporate client last year that was in the paint shop for 3 weeks.
Most agree an average of a week per plane. With 500 airplanes, that would be 9-10 years if they only did one airplane at a time (recognizing they don't paint just one airplane at a time). New airplanes, of course, will be delivered with Delta's colors if the merger is approved.
And in this video, you can see how many coats it takes:
How much does the paint on a 747 weigh?
I remember hearing somewhere they quit painting the Space Shuttle external (expendable) fuel tank and it saved 10,000lbs.
I'm not suggesting you'd stop painting airplanes, but it's still an interesting question I think.
Actually, Eastern Airlines, before it went belly up, stopped painting its airplanes. In fact, it stripped the paint OFF the airplanes nad went with polished aluminum to save weight and, hence, fuel. American Airlines now flies polished aluminum rather than painted jets.
The problem is that paint has a purpose. It protects the airplane from the corrosive effects of the environment. So whatever money you save by not having paint, you probably make up for in the cost of checmicals/maintenance.
Ty the way, the paint on a 747 weighs about 1,000 pounds.