The 737 jet will not carry passengers but will be the first flight by a U.S. carrier powered by a combination of traditional jet fuel and a biofuel. The biofuel, made from oil from the jatropha plant blended with algae, is among many alternative fuels that people are testing in hopes that they will do less damage to the environment than traditional jet fuels.

"The technical knowledge we gain today will contribute to a wider understanding of the future for transportation fuels," said Continental chairman and CEO Larry Kellner in a Wednesday statement.

The flights are the latest advances in the aviation industry's efforts to go green. Whether constructing new terminals or offering travelers ways to offset the carbon emitted from their trips by donating money to environmental projects, the industry is working to curb the notion that commercial aviation is polluting the skies.

"The simple combination of sunlight, CO2 and algae to produce a carbon-neutral, renewable fuel source has the potential to profoundly change the petrochemical landscape forever," added Jason Pyle, CEO of Sapphire Energy, the group that provided the algae oil for the Continental flight. "Today's flight puts us one step closer to moving away from fossil fuels and energy dependency, and with no impact on the transportation infrastructure, food sources or the environment."

Though the Continental flight is a first in the U.S., other airlines around the world are also working to make strides in environmentally friendly aviation.

Richard Branson tested an alternative fuel in one of his Virgin Atlantic planes last February when the carrier flew from London's Heathrow airport to Amsterdam using biofuels. Air New Zealand also recently conducted a similar test on Dec. 30, flying a 747 plane partially powered by jatropha oil.

Still, many say relying on biofuels to power flights will take some time.

-ABC News' Kate Barrett

Delta and Northwest Airlines got their holiday gift early this year in the form of a merger. As part of that, Northwest brought along pilots, flight attendants and routes.   

The new Delta also got something else: Northwest's planes, more than 320 of them. And they're all the wrong color. Now they need to be wrapped, or to be exact painted, in Delta's colors. All of those Northwest tails need a nice coat of Delta blue and Delta red.

In case you're wondering, you can't find airplane paint at Home Depot or Lowes. To complete the task, Delta went to PPG Aerospace, a company that has been selling paint to airlines for over 40 years.

Each plane requires a coat of primer to prevent corrosion of the airplanes body. Then two to three top coats are applied. The top coats are done with a polyurethane paint that provides flexibility and helps protect the airplane. In all, anywhere from 100 to 250 gallons of paint may be required to paint an airplane. Remember a Delta 747 has four engines that each produce 46,500 pounds of thrust, so you want some serious paint.

"You paint a house and 15 minutes later, it's dry," said PPG global platform business manager Paul Bowman. Bowman said that's not the case with airplanes.

According to Bowman, each coat needs to time to properly dry, between 4 and 8 hours, before the next coat can be applied.

The job also takes manpower. Five to seven workers paint an airplane at a time, with two different shifts working each day. A narrow body airplane, like one of Northwest Airlines A320's, can take four to five days to paint. Bigger planes taking longer. It's all done with paint that PPG says is less harmful to the ozone and has a lower solvent content.

Delta spokesperson Betsy Talton said the new paint jobs are "the most visible sign of integration." But it doesn't end with the paint. Until the two airlines have their operating certificates merged by the Federal Aviation Administration, the government will require pilots flying the freshly painted airplanes to include the phrase "Delta colors" when talking to air traffic controllers.   

Here's how it will work according to the FAA:

"Detroit Ground, Northwest two twenty-two with you, Delta colors."

Newly painted aircraft will also have labels on the side of the airplane that say "Operated by Northwest Airlines, Inc."

The first 747 took 12 days to repaint in Delta's signature blue and red and it could take a year to get the entire fleet repainted. 

"We are just happy the first Delta whale is ready to fly," Talton said. ("Whale" is industry slang for a 747).

If you happen to be booked on a flight to Asia the week of December 14th, you just might fly on it. 

Look for a brand new coat of paint.

-ABC News' Matt Hosford