Narrative:

An air taxi checked in north bound climbing to FL230 out of approximately FL180. I climbed the aircraft to FL270 and received the read-back. I stopped them at FL270 because there was traffic west bound at FL280. When the air taxi was approaching blh; I called traffic to both air carrier and the air taxi; clearly stating that the air taxi could expect higher when clear of that traffic. From watching the falcon I saw that the air taxi climbed from FL265 to FL275 busting their assigned altitude. At the same time; another aircraft was checking in on the far left side of my radar scope; so I did not notice the altitude violation. The air taxi climbed to FL279 and asked for higher. I then again recalled the traffic and during the transmission I realized that the air taxi was now at FL279 and not their assigned FL270. I quickly keyed up again and climbed the air taxi to their requested final altitude of FL370 with an expeditious rate. Then I descended the air carrier to FL260 to regain separation and assigned an expeditious rate. At this point the aircraft were about 8 miles apart; but converging. During this time the air taxi began to descend because I am guessing at some point they realized their mistake. It probably happened sooner; but there is a delay in the radar data; so I was working with old information. Very shortly the air carrier stated they were in an RA climb. I then told the air taxi to immediately turn 30 degrees to the left. I clearly lost my 5 mile/1000 ft separation requirement and at this point I was just trying to keep the aircraft safe and prevent a collision. From the information I gathered from the falcon; at the closest point the aircraft were about a mile and 100ft apart. I did not give the air taxi the brasher because I was quite shaken at this point; but the next controller did. If the air taxi would have just followed instructions to begin with; none of this would have happened.

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Original NASA ASRS Text

Title: ZLA Controller and two flight crews describe a serious airborne conflict which developed after an air taxi inexplicably climbed from their assigned FL270 into an air carrier at FL280. The aircraft at their closest were 100 feet vertically and about 1 mile horizontally.

Narrative: An Air Taxi checked in north bound climbing to FL230 out of approximately FL180. I climbed the aircraft to FL270 and received the read-back. I stopped them at FL270 because there was traffic west bound at FL280. When the Air Taxi was approaching BLH; I called traffic to both Air Carrier and the Air Taxi; clearly stating that the Air Taxi could expect higher when clear of that traffic. From watching the Falcon I saw that the Air Taxi climbed from FL265 to FL275 busting their assigned altitude. At the same time; another aircraft was checking in on the far left side of my radar scope; so I did not notice the altitude violation. The Air Taxi climbed to FL279 and asked for higher. I then again recalled the traffic and during the transmission I realized that the Air Taxi was now at FL279 and not their assigned FL270. I quickly keyed up again and climbed the Air Taxi to their requested final altitude of FL370 with an expeditious rate. Then I descended the Air Carrier to FL260 to regain separation and assigned an expeditious rate. At this point the aircraft were about 8 miles apart; but converging. During this time the Air Taxi began to descend because I am guessing at some point they realized their mistake. It probably happened sooner; but there is a delay in the radar data; so I was working with old information. Very shortly the Air Carrier stated they were in an RA climb. I then told the Air Taxi to immediately turn 30 degrees to the left. I clearly lost my 5 mile/1000 ft separation requirement and at this point I was just trying to keep the aircraft safe and prevent a collision. From the information I gathered from the Falcon; at the closest point the aircraft were about a mile and 100ft apart. I did not give the Air Taxi the brasher because I was quite shaken at this point; but the next controller did. If the Air Taxi would have just followed instructions to begin with; none of this would have happened.

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.