MIAMI — Southwest Airlines flew its first revenue flight with split scimitar winglets on Thursday. The Boeing 737-800 flew between Phoenix and Denver as flight 219. It will appear later today in Phoenix and Chicago.

This makes Southwest the third US airline to retrofit an aircraft with the new winglets, following United and Alaska.

In January, Southwest announced plans to order Aviation Partner’s Boeing split scimitar winglets for the carrier’s fleet of Boeing 737-800NG aircraft. The airline ordered 85 pairs to retrofit the 52 Boeing 737-800s currently in its fleet as well as the 33 Boeing 737-800s it plans to take delivery of this year.

The winglets boast a new design with aerodynamic scimitar tips with a large ventral strake on the bottom of the blended winglet structure.

With the new winglet design, Southwest spokesperson Dan Landson, says “We are always looking at ways to reduce our fuel costs and reduce consumption of fuel. With the new split scimitar winglets, we estimate our fuel savings will be increased by 5 to 5.5% from 3.5% with the current blended winglet structure. Not only are the savings large but it’s impact on the environment is much better since we’re using less fuel.”

Southwest expects all of its Boeing 737-800s to receive the retrofit by early 2015. Presently it only has just the one.