Narrative:

Scheduled flight from jfk to lhr to bru. Departed jfk in the evening arriving lhr in morning. Departed for brussels 1 1/2 hours later with copilot flying. Cleared to descend to 7000' by brussels control. Nearing 7000' captain was listening to ATIS, 3RD officer was talking to company and the copilot reported clearance to 2000' with a frequency change. At this time I was flying, communicating and navigating. At 5500' we entered a scattered group of clouds and went IFR when captain returned to frequency and simultaneously center queried our altitude. Captain asked me if we were cleared to 2000'. I said 'yes' and he told center we were descending to 2000'. Center said 'negative.' who cleared you? We stated the other controller and center told us to turn right to 180 degree (we were heading approximately 100 degree) as we turned and descended we popped out of the clouds around 4000' and saw a foreign air force mlt in a climbing right turn at our 11:30 position. An uneventful landing was accomplished. Tapes are requested for review. Fatigue, language barriers, heavy traffic in terminal area and multiple duties of crew other than only monitoring the aircraft are all contributing factors in my opinion. Supplemental information from acn 90843. During descent into bru area our clearance was to 7000. Approaching 7000 I returned ATIS for update after copying ATIS I returned my attention to cockpit and saw 2000' set in altitude reminder. As we were descending thru approximately 5000' bru ATC asked 'what altitude were we descending to.' I responded '2000'', ATC reply was 'who cleared you to 2000'?' I answered 'previous controller' (getting a visual agreement from first officer). My guess is that we responded to another aircraft clearance without rechallenge by ATC.

Related reports:

Google
 

Original NASA ASRS Text

Title: CLOSE PROX ACR WDB FOREIGN AIR FORCE MLT NEAR BRU.

Narrative: SCHEDULED FLT FROM JFK TO LHR TO BRU. DEPARTED JFK IN THE EVENING ARRIVING LHR IN MORNING. DEPARTED FOR BRUSSELS 1 1/2 HOURS LATER WITH COPLT FLYING. CLRED TO DSND TO 7000' BY BRUSSELS CTL. NEARING 7000' CAPT WAS LISTENING TO ATIS, 3RD OFFICER WAS TALKING TO COMPANY AND THE COPLT RPTED CLRNC TO 2000' WITH A FREQ CHANGE. AT THIS TIME I WAS FLYING, COMMUNICATING AND NAVIGATING. AT 5500' WE ENTERED A SCATTERED GROUP OF CLOUDS AND WENT IFR WHEN CAPT RETURNED TO FREQ AND SIMULTANEOUSLY CENTER QUERIED OUR ALT. CAPT ASKED ME IF WE WERE CLRED TO 2000'. I SAID 'YES' AND HE TOLD CENTER WE WERE DSNDING TO 2000'. CENTER SAID 'NEGATIVE.' WHO CLRED YOU? WE STATED THE OTHER CTLR AND CENTER TOLD US TO TURN RIGHT TO 180 DEG (WE WERE HDG APPROX 100 DEG) AS WE TURNED AND DSNDED WE POPPED OUT OF THE CLOUDS AROUND 4000' AND SAW A FOREIGN AIR FORCE MLT IN A CLBING RIGHT TURN AT OUR 11:30 POS. AN UNEVENTFUL LNDG WAS ACCOMPLISHED. TAPES ARE REQUESTED FOR REVIEW. FATIGUE, LANGUAGE BARRIERS, HEAVY TFC IN TERMINAL AREA AND MULTIPLE DUTIES OF CREW OTHER THAN ONLY MONITORING THE ACFT ARE ALL CONTRIBUTING FACTORS IN MY OPINION. SUPPLEMENTAL INFO FROM ACN 90843. DURING DSCNT INTO BRU AREA OUR CLRNC WAS TO 7000. APCHING 7000 I RETURNED ATIS FOR UPDATE AFTER COPYING ATIS I RETURNED MY ATTN TO COCKPIT AND SAW 2000' SET IN ALT REMINDER. AS WE WERE DSNDING THRU APPROX 5000' BRU ATC ASKED 'WHAT ALT WERE WE DSNDING TO.' I RESPONDED '2000'', ATC REPLY WAS 'WHO CLRED YOU TO 2000'?' I ANSWERED 'PREVIOUS CTLR' (GETTING A VISUAL AGREEMENT FROM F/O). MY GUESS IS THAT WE RESPONDED TO ANOTHER ACFT CLRNC WITHOUT RECHALLENGE BY ATC.

Data retrieved from NASA's ASRS site as of August 2007 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.