A330
Air Traffic Control Fully Certified
Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors
While working Sectors XX/YY/ZZ/WW combined; an A330 was at FL320 and requested a climb to FL340. He was cruising at M0.81 and had an aircraft 8 minutes ahead of him at FL330 cruising at M0.79. I advised the A330 that I was unable higher due to traffic; however; I advised the A330 that higher would be available with a climb at M0.76 to resume M0.81 upon reaching FL340. An A330 acknowledged that advisory but did not request the advised climb. Six minutes later; the A330 then requested to know when to expect a higher altitude. I advised the A330 that he had traffic one thousand feet above him that is M0.03 slower than him and at M0.76 he could climb to FL340 now; otherwise I could offer a reroute. The A330 acknowledged the advisory. And immediately after acknowledging the advisory sent a transmission that he was climbing to FL340. I demanded his ADS; his altitude indicated that he was in a climb for FL340; and a trail probe went off with the aircraft in front of him at FL330. He sent a transmission indicating he was leveling at FL340; and I advised him that I had not sent a clearance to him and cleared him to maintain FL340. I believe the situation could have been avoided had I not used the words 'you can climb now' when answering his question as to when he can expect a higher altitude. I believe the language barrier had something to do with it. Also; the A330 should have verified if I had sent him a clearance or not; and waited until I sent an actual clearance to FL340. I would recommend being more clear and concise when dealing with foreign language speaking pilots.
Enroute Controller working non-RADAR oceanic traffic described an unauthorized climb through occupied airspace; the reporter acknowledging using less than clear and concise phraseology with this international flight crew.