Date: 201504
Local time of day: 1201-1800
Location: ZDV.ARTCC, CO
Light: Daylight
Aircraft: Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZDV
ATC / advisory: Center ZDV
Reporter organization: Government
Reporter function: Enroute; Trainee
Reporter qualification: Air Traffic Control Developmental
Human factors: Confusion; Communication Breakdown; Distraction; Troubleshooting; Situational Awareness
Second reporter function: Instructor; Enroute
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure
Primary problem: Procedure

Narrative: I was training on the RADAR position on sector 30.  Traffic was light and not complex.  Aircraft X checked in westbound at FL340 and then shortly after I acknowledged the check in; he reported that he had just seen a weather balloon pass directly beneath his flight path about 1;000 feet below.  The sector team had not been made aware that a weather balloon without a transponder was to be launched anywhere near our airspace; but it turned up on my boundary with another sector at approximately FL330.  We notified the supervisor who was aware of the balloon but not the exact whereabouts because it was not equipped with a transponder.  He did come back to the sector team with much more information about the balloon but after the aircraft had already reported passing over it.  The pilot then advised me that he would recommend that we provide vectors to any other aircraft flying through the area.  This is an unsafe situation because we have weather balloons that we cannot identify with the radar that are climbing and descending through air traffic without us having any knowledge of where they are actually at in real time or what altitude they are at.  We were told that the operators had a waiver in which a transponder was not required because of the size; but the concern of the pilot leads me to believe that no pilot would want to hit one of those balloons cruising at FL 340.  There is prescribed phraseology in the 7110.65 about unmanned balloon operations but the verbiage is vague; and ties our hands since a pilot can request a vector around the area where the balloon last was; but we don't know where it is in real time so we could actually be vectoring the aircraft in the path of the balloon without knowing it.  Many people in the facility believe this to be a problem and we've seen many balloons go up and come down without issue; but after hearing the pilot's concern and myself and my trainer having no previous knowledge of it; I believe there need to be changes to the procedures regarding weather balloons.I believe that all weather balloons should be equipped with a transponder so we know the exact location and altitude because then we could actually provide a helpful vector to aircraft that request it.  We can also advise aircraft more accurately.


Second narrative: Aircraft X was at FL340 westbound. He checked on frequency stating that a weather balloon had just passed right below them by about 1;000 feet.  It had a lot of stuff hanging off it and advised if anyone else went through that area; they should be vectored around it. You could tell the pilot was upset by this.  At this point; I was training the R-side so I had him ask the supervisor if we knew anything about a weather balloon. We were informed that there was one in that area climbing to FL890 that did not have/require a transponder.  We informed all aircraft in the area of it; and advised if they would like vectors around the area ask; but; we cannot see the balloon on radar.I recommend the FAA to stop issuing waivers to balloons without transponders. I have worked multiple situations with balloons that have transponders which make traffic calls much easier and practical.  Pilots appreciate this information; as it seems unnerving for them to fly through a large balloon.  It is unsafe to have balloons as large as these fly through our airspace without us having any way to track them.


Synopsis: ZDV Controllers reports that an aircraft under his control reported a balloon at FL350. The controller did not know anything about the balloon but the FLM was aware of the balloon.