Date: 201408
Local time of day: 1201-1800
Location: ZMP.ARTCC, MN
Light: Daylight
Aircraft: Fighter
Operator: Military
Operating under: Part 91
Flight plan: IFR
Mission: Tactical
Flight phase: Climb
Airspace: Class E ZMP
ATC / advisory: Center ZMP
Second aircraft: Large Transport
Reporter organization: Government
Reporter function: Enroute; Supervisor / CIC
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Communication Breakdown; Situational Awareness
Second reporter function: Enroute
Anomaly: Conflict Airborne Conflict; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Separated Traffic
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Procedure

Narrative: Small area of thunderstorms about 20 miles SE of OVR.  Aircraft X; flight of six; departed OMA; and appeared to be on course direct IRK.  Aircraft Y departed OMA a few minutes later; on course direct JALAP.  Both routes put aircraft in close proximity to thunderstorm.  Aircraft X flight was about 7 or so miles in trail; non standard; with the trailing aircraft squawking 4000; but no Mode C; and was significantly slower than Aircraft Y.  The aircraft between the lead and trail aircraft were primary only.  Controller cleared Aircraft X direct destination; which appeared to keep the flight north of the route of Aircraft Y; as well as clear of the thunderstorm.  Aircraft X was cleared by the Section 27 Controller to 190B210.  The trailing aircraft was lower than the lead aircraft; who was the only one in the flight with his Mode C turned on.  Aircraft Y checked on with the Sector 27 Controller climbing to 150; as per standard procedures.  When Aircraft Y stated that he needed to deviate for the thunderstorm; the Section 27 Controller immediately started calling traffic with the trailing aircraft in the Aircraft X flight; as well as ask the Aircraft X flight lead what the altitude of the trailing aircraft was.  Aircraft Y reported the aircraft in sight; and the flight lead reported that the trailing aircraft was above Aircraft Y by more than a thousand feet. The targets of the trailing aircraft and Aircraft Y merged; or were very close to merging.It seems that OMA Approach cleared Aircraft Y to an altitude and on a route that did not guarantee that necessary separation would remain between the Aircraft X flight and Aircraft Y.  Both aircraft were cleared on a route that put them very near or into a known thunderstorm; for which many aircraft had already deviated from their assigned route.  Also; because the Aircraft X flight was significantly slower in comparison to Aircraft Y; this was an overtake situation.  Additionally; the Aircraft X flight was non standard; many miles in trail.  This had the potential to put Aircraft Y in very close proximity with one or more of the aircraft in the flight.  My suggestion is that; in this case; OMA Approach should have assigned Aircraft Y and Aircraft X flight either headings or routes that clearly met approved separation standards; as well as keep the aircraft clear of the known thunderstorm.  This would allow the Section 27 controller to climb Aircraft Y above the flight; at which point the aircraft could join their assigned routes.  The attempted use of vertical separation; with the large difference in speed (much faster behind) and when the trail aircraft of a flight of six is not squawking Mode C; in this case; caused an uncontrolled situation and had the potential to put these aircraft too close together.


Second narrative: Aircraft X was a flight of 6 [aircraft] off of OMA.  They checked on climbing to block 130b150; I cleared them to climb to 190b210.  They were 5 miles in trail front to back; the back [aircraft] was squawking 4000 without an altitude readout.  Aircraft Y was departing OMA climbing to 150 when he checked on and requested to deviate left; into the flight.  The lead [aircraft of the flight] was climbing well; he was out of 17;000; unfortunately the last [aircraft] was not climbing well; he was only out of 14;000 climbing to FL190b210. Aircraft Y was not cleared to deviate; but he had to go left in order to avoid a storm.  I called the traffic and Aircraft Y reported seeing the flight; I instructed for him to maintain visual separation from the climbing flight and he complied.  Long story short Aircraft Y got within a mile or two and at or about the same altitude prior to being instructed to maintain visual separation from the flight.  I had to keep inquiring as to the last aircrafts altitude in order to reestablish vertical separation prior to turning Aircraft Y on course and climbing them.If a formation flight of numerous aircraft will not be in close proximity to one another or will climb at different rates then they should file separate flight plans or be instructed to all climb at roughly the same rate so as to not have the aircraft that is the data block is associated with show level flight and the rest of the formation be 3;000 to 5;000 feet lower or higher.


Synopsis: ZMP FLM and Controller report of a non-standard flight being overtaken by speed of a trailing aircraft.