A controller reported a loss of separation following a military formation flight break up.

Attributes
ACN	1455176
Time
Date	201706
Local Time Of Day	1201-1800
Place
Locale Reference	ZDV.ARTCC
State Reference	CO
Aircraft 1
Make Model Name	Stratotanker 135
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Aircraft 2
Make Model Name	Fighting Falcon F16
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Enroute Handoff / Assist
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 2
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

Narrative:

I was on the radar assist position and the person working the radar was conducting a flight break up. Aircraft X and aircraft Y completed their refueling mission and requested the break up from fl200b230. The radar controller had aircraft Y come up on frequency and reported level at 22000 ft. Aircraft X also reported level at 22000 ft. The radar controller radar identified aircraft Y and instructed the aircraft to descend to 21000 ft. The loss of separation occurred since ATC instructed aircraft Y to descend instead of the flight leader; aircraft X. We all need to have a full understanding of the procedures when conducting a flight break-up/join. ATC cannot issue a control instruction if standard separation isn't first met. The controller must only relay instructions through the flight leader until standard separation is gained.

Original NASA ASRS Text

Title: A Controller reported a loss of separation following a military formation flight break up.

Narrative: I was on the Radar Assist position and the person working the Radar was conducting a flight break up. Aircraft X and Aircraft Y completed their refueling mission and requested the break up from FL200B230. The Radar Controller had Aircraft Y come up on frequency and reported level at 22000 ft. Aircraft X also reported level at 22000 ft. The radar Controller radar identified Aircraft Y and instructed the aircraft to descend to 21000 ft. The loss of separation occurred since ATC instructed Aircraft Y to descend instead of the flight leader; Aircraft X. We all need to have a full understanding of the procedures when conducting a flight break-up/join. ATC cannot issue a control instruction if standard separation isn't first met. The controller must only relay instructions through the flight leader until standard separation is gained.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.