The National Guard Bureau plans to discontinue its “Operation Snowbird” visitor pilot training program, according to documents filed this week in a federal lawsuit aimed at stopping expansion of that program and other training at Davis-Monthan Air Force Base.

A May 23 memorandum from the chief of airspace and ranges for the Air Guard states that the bureau will pull funding for Operation Snowbird operations support squadrons at D-M at the end of the 2017 fiscal year, according to a stipulation cited in the suit that’s signed by the Air Force and residents who filed the lawsuit to stop the training expansion.

“Due to reductions in Air National Guard participation in the OSB program, the return of investment of continuing (Operation Snowbird) has fallen below a reasonable threshold,” Col. Brian K. Lehew wrote.

The memo said the decision, made “as part of an overall reassessment of Air National Guard training requirements,” will end support for Operation Snowbird facilities at D-M, possibly impacting other D-M training that used logistical support from the Snowbird office.

Though the Air National Guard 162nd Wing is based at Tucson International Airport, a detachment from the wing is based at permanent Operation Snowbird facilities at D-M.

Operation Snowbird was originally started in 1975 to give National Guard units from colder climates a place to train in the winter, taking advantage of Southern Arizona’s warm weather and abundant nearby training ranges.

The 162nd Wing at TIA is the Guard’s biggest F-16 fighter training base and is a center of training for F-16 pilots from allied nations including Iraq and the Netherlands.

A few years ago, the Air Force proposed increasing the maximum number of training flights at D-M, including Operation Snowbird and other active-duty and reserve training under the umbrella of umbrella of “Total Force Training.”

The Air Force plan would increase annual training sorties at D-M by as much as 65 percent from a 2009 baseline, to up to 2,326 training sorties per year.

Three Tucson residents filed a federal lawsuit in January 2016, alleging the Air Force failed to follow federal law and Pentagon policy in finding that the expansion of the Total Force Training program would have no significant impact on the community.

That lawsuit in the U.S District Court for Arizona has yet to reach hearings. 

But on Monday, U.S. Magistrate Judge Jacqueline Rateau approved a stipulated order suspending the schedule for filing legal briefs in the case, while the Air Force finalizes a decision on Operation Snowbird and related training.

The order requires the parties in the case to file a status report within 60 days.