After 25 years of striving to reintroduce whooping cranes into the eastern section of North America, Operation Migration will cease work at the end of 2018.

"This difficult decision to dissolve the organization is heartbreaking for us all, but we have exhausted all possible avenues to avoid this outcome," said Joe Duff, CEO and co-founder of Operation Migration headquartered in Port Perry, Ontario, in a written statement.

"We continued our work based upon our belief that the goal of a self-sustaining Eastern Migratory Population of Whooping Cranes was attainable, however, with new management directives authorized by the Whooping Crane Recovery Team and implemented by Region 3 Fish and Wildlife service, we no longer believe this goal is achievable."

Beginning with the first migratory flight out of Wisconsin's Green Lake County in 2001, Operation Migration trained young whooping cranes to imprint on human beings, then follow them as they flew an ultra-light airplane from Wisconsin to Florida and back.

The goal for Duff and Bill LIshman, who developed the aircraft-guided migration method, was to reintroduce whooping cranes into an area that they had not inhabited in over a century. Their work helped establish a distinct population of whooping cranes, separate from the natural flock living in Western North America.

For 15 years, Operation Migration pilots and ground crew led cranes on survival flights that covered 17,457 miles with a total of 186 whooping cranes following the plane.

Their efforts received awards from the National Wildlife Federation, the Whooping Crane Conservation Association, the American Birding Association, and the U.S. Department of the Interior.

Celebrities such as former President Jimmy Carter and conservationist Jane Goodall supported their work to create more awareness of the situation for whooping cranes and help foster the flock in eastern North America.

Planes used in Operation Migration are on display at Disney's Animal Kingdom, the Smithsonian Air and Space Museum, and the Experimental Aircraft Association Museum.

Operation Migration carried out aircraft-led migration flights until 2015 when the U.S. Fish and Wildlife Service decided the method was "too artificial." After ending the flights, Operation Migration continued research on whooping cranes including costume rearing, releasing parent-reared cranes, and helping to track and monitor the eastern flock.

With the new management directives in place, Duff said that "we cannot continue, in good faith, to accept contributions or assign our staff and volunteers to carry out the work outlines in the strategic plan imposed on the Whooping Crane Eastern Partnership."