Washington (CNN) The US Air Force has ordered a one-day standdown for an "operational safety review" following a series of recent accidents and fatalities involving military aircraft -- including an incident last week that killed nine crew members of a WC-130 cargo plane -- according to a statement by the Air Force on Tuesday.

Units will be expected to fulfill the review at different times to ensure safety and continued operations.

Units involved in combat operations in places like Iraq, Syria and Afghanistan may be exempted from the standdown but will conduct a review, Maj. Gen. John Rauch, the Air Force chief of safety, told reporters Tuesday.

The Chief of Staff of the Air Force Gen. David L. Goldfein ordered the units to execute the one-day operational safety review by May 21, 2018.

Reserve and Air National Guard units will have until June 25 to complete the review.

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