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A group that trains and leads endangered whooping cranes with ultralight aircraft will be allowed to continue this year after the practice had been called into question during the 2011-’12 migration.

The Federal Aviation Administration has agreed to grant an exemption for the next two years to Operation Migration – a group that has been leading whooping cranes to Florida from Wisconsin since 2001.

The decision clears a major hurdle to re-establish a migrating flock of whooping cranes in the eastern United States.

“We are very grateful to everyone for all the support we received, and to the FAA for understanding how important this project is to conservation of Whooping cranes - and to the thousands of people who follow it,” Joe Duff, co-founder of the Operation Migration wrote recently on the group’s website.

Operation Migration halted operations for a time in January because the FAA raised questions about the practice of using lightweight planes for leading cranes. The migration was abandoned altogether in early February after it was determined that the 2011-’12 trip to Florida was taking too long.

The cranes then spent the winter at the Wheeler National Wildlife Refuge in Alabama.

Problems with regulators arose after a former pilot filed a complaint with the FAA. Pilots of small aircraft such as those used to lead the cranes are prohibited from being compensated for their work. The pilots for Operation Migration were paid for their work on the ground, but not while they flew.

The FAA concluded that granting an exemption was in the public interest since the ultralights are used to train juvenile cranes for migration, and then lead the birds south. The cranes are able to return north on their own, or fly with other older cranes.

In granting the exemption, the FAA said the pilots would need to upgrade from light sport aircraft certificates to private licenses.

Also, Operation Migration may have to upgrade its planes from experimental light sport aircraft to special light sport aircraft, which resembles a traditional single-engine plane. Duff said on the Operation Migration website that special light sport aircraft fly faster than the speeds needed to lead cranes.

“We will have to work with a manufacturer to redesign an aircraft to be lighter and fly slower yet still fit into the special category,” he said.