MD88 ACFT WITH CLRNC FOR DSCNT WAS THEN CLRED TO FL210 FOR HOLDING AFTER ACFT HAD ALREADY DSNDED TO FL198. FLC IMMEDIATELY CLBED BACK TO NEW ASSIGNED ALT.

Narrative

CONFUSION OVER ALT ASSIGNMENT. FLT WAS CLRED TO CROSS LENDY AT FL190; EXPECT ILS RWY 4R JFK. APPROX 12 MI FROM LENDY; WHILE DSNDING THROUGH FL207; WE WERE CLRED TO HOLD AT LENDY AS PUBLISHED AT FL210; SPD OUR DISCRETION; EXPECT ILS RWY 31R JFK. WE VERIFIED OUR ASSIGNED ALT AS WE LEVELED OFF AT FL198. NYC CONFIRMED FL210 AND WE INITIATED AN EXPEDITED CLB TO FL210; AND ENTERED HOLDING AT LENDY AT FL210. CONTRIBUTING FACTORS: 1) RADIO CONGESTION. WE WERE THE THIRD ACFT ISSUED HOLDING AT LENDY IN QUICK SUCCESSION. ANOTHER ACFT WAS CALLING CTR TO RPT DEVIATING FOR TCASII CONFLICT. 2) CREW WAS IN THE SEVENTH HR OF FLT TIME FOR THE DAY. 3) NIGHT. 4) ANOTHER ACFT WAS THOUGHT TO BE GIVEN THE SAME HOLDING CLRNC AT FL210. 5) ONE PLT WAS LOOKING UP PUBLISHED HOLDING AT LENDY AND SETTING UP WHILE OTHER PLT WAS COPYING AND READING BACK HOLDING CLRNC WITH CONGESTED RADIO FREQ. PROB WAS DISCOVERED -- CREW DISAGREEMENT OF ASSIGNED ALT OF FL190 VERSUS FL210; SINCE CLRNC LIMIT ALT WAS ASSIGNED AFTER DSNDING THROUGH IT ON WAY TO PREVIOUS CLRNC LIMIT ALT OF FL190. CORRECTIVE ACTION: IMMEDIATE LEVELOFF; AND SIMULTANEOUS QUERY OF ATC CTLR BY AIR CREW. RAPID CLB TO FL210 AFTER VERIFICATION BY ATC. AIR CREW CLRING FOR OTHER ACFT VIA VISUAL AND TCASII OPS AT 10 MI RANGE. HUMAN PERFORMANCE CONSIDERATION: 1) LONG DAY OF FLYING; CREW WAS IN SEVENTH HR OF FLT TIME; INTO A HIGH DENSITY AREA. 2) ATC CTLR WAS TASK SATURATED DUE TO THE CHANGE OF RWY AT DEST ARPT; AND NUMBER OF ACFT ON FREQ TRYING TO CONFIRM HOLDING INSTRUCTIONS AND DEVS.