Narrative:

On descent, ott 3 arrival into bwi, we received a clearance to FL200. We acknowledged and read back FL200 and even pointed and said to each other FL200. Even the jump seat rider heard and saw us put in FL200 into the altitude window. He is an air carrier B737 pilot based in bwi, and familiar with the route flown. Passing FL210, the controller asked what altitude we were cleared to. The first officer said FL200. The controller said it was FL220. I first looked at the TCASII and there was no traffic at all on the screen. A min passed, he turned us 20-30 degrees. A min or so later, another voice came on and apologized and said that we were cleared to FL200 and cleared us back on course. I believe that since there are more planes in the air than ever before, all controllers should listen to all altitude readbacks! This could have been avoided if he heard us read back FL200. I always keep a speaker on if we have a jump seat rider. Just as an extra precautionary measure, we do our part in the cockpit. I would like to think that everybody else is doing theirs.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR B737 RECEIVES DSCNT CLRNC TO FL200. ZDC CTLR CHALLENGES ASSIGNED ALT AS FLC DSNDS THROUGH FL210. SHORTLY, ATC ACKNOWLEDGES ORIGINAL CLRNC WAS CORRECT.

Narrative: ON DSCNT, OTT 3 ARR INTO BWI, WE RECEIVED A CLRNC TO FL200. WE ACKNOWLEDGED AND READ BACK FL200 AND EVEN POINTED AND SAID TO EACH OTHER FL200. EVEN THE JUMP SEAT RIDER HEARD AND SAW US PUT IN FL200 INTO THE ALT WINDOW. HE IS AN ACR B737 PLT BASED IN BWI, AND FAMILIAR WITH THE RTE FLOWN. PASSING FL210, THE CTLR ASKED WHAT ALT WE WERE CLRED TO. THE FO SAID FL200. THE CTLR SAID IT WAS FL220. I FIRST LOOKED AT THE TCASII AND THERE WAS NO TFC AT ALL ON THE SCREEN. A MIN PASSED, HE TURNED US 20-30 DEGS. A MIN OR SO LATER, ANOTHER VOICE CAME ON AND APOLOGIZED AND SAID THAT WE WERE CLRED TO FL200 AND CLRED US BACK ON COURSE. I BELIEVE THAT SINCE THERE ARE MORE PLANES IN THE AIR THAN EVER BEFORE, ALL CTLRS SHOULD LISTEN TO ALL ALT READBACKS! THIS COULD HAVE BEEN AVOIDED IF HE HEARD US READ BACK FL200. I ALWAYS KEEP A SPEAKER ON IF WE HAVE A JUMP SEAT RIDER. JUST AS AN EXTRA PRECAUTIONARY MEASURE, WE DO OUR PART IN THE COCKPIT. I WOULD LIKE TO THINK THAT EVERYBODY ELSE IS DOING THEIRS.

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