Narrative:

Air carrier X level at FL360 had multiple crossing traffic at his altitude. I asked him if he could accept FL380 for traffic. His response was unintelligible to me. I told him that I missed his response and asked him if he said affirmative to being able to accept FL380. He said; 'copy.' I told him; 'roger; I will have that for you in a couple minutes; standby.' approximately one minute later; conflict alert was activated and showed air carrier X at FL365. I told him to maintain FL360; I had never issued him a climb clearance. I issued a traffic alert and told him to descend immediately. Air carrier X lost separation with air carrier Y at FL370 and air carrier Z at FL370. I never issued a climb clearance to air carrier X; nor did he ever read back an altitude change. When I told him I would have an altitude change for him in a couple minutes and to standby; he never responded at all. Air carrier Z did get a TCAS RA. I issued the traffic to him and told him that air carrier X was descending out of FL370 which is what the radar indicated. Air carrier Z never left FL370. What led to this event was me asking the pilot if he could accept a higher altitude for traffic; questioning his response when it was unreadable; I verified he could accept FL380; [and] then told him I would have it for him in a couple minutes and to standby. This event happened because the pilot was never issued an altitude change; never read back an altitude assignment; but left FL360 and climbed through two other aircraft at FL370. I told him I would have the altitude change in a couple of minutes because I was fully aware of the two aircraft passing him at FL370. During further discussion with the pilot on the frequency he claims he heard 'expedite' instead of 'expect' when I never in fact used the word 'expect' at all in the initial transmissions to him; I told him I would have it for him in a couple minutes. This is very blatant pilot deviation which put three aircraft in very close proximity to each other. I am deeply concerned about why a pilot would leave their altitude without a clearance to do so; and why he would climb to a new altitude without ever reading the clearance back to me. Why was this not caught or questioned by either the pilot or co-pilot? My recommendation would be for a pilot to always read back an altitude change; and for the pilot and co-pilot to check each other when issued an altitude change; which I believe is standard procedure for most airlines. If the pilot was alone in the cockpit; he should have asked me to verify the altitude again; which I believe is airline procedure also. If the pilot would have looked at his TCAS display prior to leaving FL360 he would have seen two aircraft in his immediate vicinity at FL370; and should have questioned what he thought was a clearance to FL380. Any of these actions by the pilot would have prevented this incident from occurring.

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Original NASA ASRS Text

Title: Enroute Controller described a loss of separation event involving several aircraft. The reporter indicated the pilot started an unauthorized climb after being advised of the Controllers' plans.

Narrative: Air Carrier X level at FL360 had multiple crossing traffic at his altitude. I asked him if he could accept FL380 for traffic. His response was unintelligible to me. I told him that I missed his response and asked him if he said affirmative to being able to accept FL380. He said; 'Copy.' I told him; 'Roger; I will have that for you in a couple minutes; standby.' Approximately one minute later; Conflict Alert was activated and showed Air Carrier X at FL365. I told him to maintain FL360; I had never issued him a climb clearance. I issued a traffic alert and told him to descend immediately. Air Carrier X lost separation with Air Carrier Y at FL370 and Air Carrier Z at FL370. I never issued a climb clearance to Air Carrier X; nor did he ever read back an altitude change. When I told him I would have an altitude change for him in a couple minutes and to standby; he never responded at all. Air Carrier Z did get a TCAS RA. I issued the traffic to him and told him that Air Carrier X was descending out of FL370 which is what the RADAR indicated. Air Carrier Z never left FL370. What led to this event was me asking the pilot if he could accept a higher altitude for traffic; questioning his response when it was unreadable; I verified he could accept FL380; [and] then told him I would have it for him in a couple minutes and to standby. This event happened because the pilot was never issued an altitude change; never read back an altitude assignment; but left FL360 and climbed through two other aircraft at FL370. I told him I would have the altitude change in a couple of minutes because I was fully aware of the two aircraft passing him at FL370. During further discussion with the pilot on the frequency he claims he heard 'expedite' instead of 'expect' when I never in fact used the word 'expect' at all in the initial transmissions to him; I told him I would have it for him in a couple minutes. This is very blatant pilot deviation which put three aircraft in very close proximity to each other. I am deeply concerned about why a pilot would leave their altitude without a clearance to do so; and why he would climb to a new altitude without ever reading the clearance back to me. Why was this not caught or questioned by either the pilot or co-pilot? My recommendation would be for a pilot to always read back an altitude change; and for the pilot and co-pilot to check each other when issued an altitude change; which I believe is standard procedure for most airlines. If the pilot was alone in the cockpit; he should have asked me to verify the altitude again; which I believe is airline procedure also. If the pilot would have looked at his TCAS display prior to leaving FL360 he would have seen two aircraft in his immediate vicinity at FL370; and should have questioned what he thought was a clearance to FL380. Any of these actions by the pilot would have prevented this incident from occurring.

Data retrieved from NASA's ASRS site as of July 2013 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.