A small study facilitated by American Airlines and Google has shown that it's relatively easy to cut the amount of contrails created by airliners but it comes at a fuel penalty. American supplied the aircraft for 70 flights and used software developed by Breakthrough Energy to create flight plans that avoided frozen water vapor-producing conditions. In the trial they were able to reduce contrails by 54 percent but maneuvering to avoid the contrail conditions used about 2 percent more fuel. And even though more fuel was used, the contrail avoidance might be worth it from an environmental point of view, according to the authors of the study.
This is a companion discussion topic for the original entry at https://www.avweb.com/aviation-news/contrail-avoidance-possible-but-uses-more-fuel