Date: 201603
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Stratotanker 135
Operator: Military
Operating under: Part 91
Flight plan: IFR
Mission: Refueling
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Second aircraft: Stratotanker 135
Reporter organization: Military
Reporter function: Instructor; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Instrument
Human factors: Situational Awareness; Communication Breakdown; Confusion
Second reporter function: Captain; Pilot Flying
Anomaly: Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: At the completion of an Air Refueling event we split up from the formation we were in and climbed to the top of the formation block altitude (FL260). The number two aircraft who was still refueling with the receiver coordinated random Air Refueling clearance from Center to proceed direct to ZZZ. After number two coordinated their clearance we coordinated for direct ZZZZZ intersection and flight plan route and received a clearance to climb to FL280 and proceed direct to ZZZZZ intersection. Approximately 3 minutes after level off we receive a TA and saw a TCAS target at our altitude. At the same time we received a radio call from ATC to turn immediately to a heading of 090 which we complied with. This de-conflicted the traffic and we subsequently were given direct to ZZZZZ intersection.


Second narrative: I was part of a formation of 2 KC-135R tankers. I originally took off as lead with my wingman as FLT2. We entered the MOA in the block 24-26 to refuel with an aircraft. Once we were in the area; I did a position change with FLT2 and turned my Mode 3 to standby once I was no longer the lead aircraft. At the conclusion of air refueling; I went to the top of the block and let lead work his clearance to drag the aircraft to ZZZ for random refueling while we requested to go flight plan route to ZZZ1. We went to the top of the block and were radar identified by ATC. We were given FL280 and direct ZZZ1. About 1 minute later we received a call to turn immediately to 090 about the same time I got a TA on TCAS. What I believe caused the TA was confusion on who was squawking once we did the lead change. I believe the controller thought that we were FLT2 going to ZZZ at 280. Our clearance on takeoff had a discrete squawk for FLT2 for takeoff and transit out to the area (although he is in standby unless we get separated) and a second squawk for when we split up in the MOA and return as single ship back to base. I believe the confusion occurred when FLT2 became lead and turned on his Mode 3 and I turned mine to standby. The radar identification of my wingman at a lower altitude and me 1000 ft above him should have been enough to regain SA for the controller but still the confusion persisted. Our two aircraft were going in different directions which should have also helped to resolve who was who (FLT2 and the aircraft it was dragging were cleared direct ZZZ and we were cleared direct ZZZ1 (about 50 degrees apart course wise). We ended up making a 30 degree angle of bank turn to 090 and descended to 270 as directed and returned to an uneventful landing.


Synopsis: KC-135 crew reported an RA after the conclusion of a formation air refueling mission perhaps due to some confusion by ATC.