Narrative:

We were at cruise at FL260 on the big sur 2 arrival near prb headed to sfo. Big sur VOR was the next fix on the arrival that we were flying to. I was the non-flying pilot handling the radios and monitoring my first officer (first officer) who was flying the aircraft. We were assigned by ATC to descend to FL200. I read back the descent clearance to FL200 and our call sign. There was no read back from ATC that we had the wrong clearance and my first officer initiated a descent to FL200. A few moments later ATC asked us if we were maintaining FL260. I told the controller; no; that we were descending to FL200 as instructed. He told us the descent was for another aircraft and that we were to maintain FL240. We were slightly below FL240 so my first officer quickly dialed in FL240 in the altitude alerter and put the aircraft into a vertical speed climb. We captured and maintained FL240 and very shortly there after ATC then issued a new clearance; a pilot's discretion descent to FL200. I believe the controller told us later that the descent was for another company aircraft. I'm not sure where the mistake was made whether we took another aircraft's clearance or if ATC got confused. The call signs became a problem again when we got on nct and were being vectored for spacing into sfo. I believe our company was ahead of us on the arrival and the approach controller got confused with our call signs. There was again confusion on a heading change assigned to one of us; a 260 heading to 360 if I remember correctly.I believe the event occurred because we do not have a program that identifies similar sounding call signs. Our company should take a hard look at flight numbers that are similar operating in the same geographic location. It's one thing to have an aircraft flying on the west coast and a similar call sign flying on the east. But when there are similar numbers jumbled slightly differently; both flying into the same hub at the same time; problems can occur.suggestions: obviously vigilance and a sharp ear is key; but I find it somewhat annoying that we have such similar sounding call signs flying near each other. The program of adding an alphabetical letter to a number which is nothing like the flight number is not working and has its own set of problems. In my opinion; that program should go too. There has to be a simple software program that can analyze assigned flight numbers in geographic areas and identify similar sounding call signs. If not that; then let's drop either the first or last number off the flight number. [There are] two reasons I say to do it that way: 1) because it is similar enough that we as crew still associate it to the flight we are actually flying. Many of us clip our trip sheet to the yoke or somewhere else in the cockpit and reference it as we identify incoming calls or transmit to ATC. We fly many flights a day and unfortunately can't memorize each flight number for every segment. Also the flight number we input into ACARS is the number as designated by the company. We can change it after the fact; but then that can cause confusion in ACARS. 2) to keep our brains on the same page it can be difficult to recall two different flight numbers; one to recite to the passengers; operations; gate agents; etc. And the other to ATC. If our company really wants to add a letter to the end of a call sign I would recommend adding it to some segment of the flight number. That way we keep some part of the flight number and can distinguish it from other similar call signs that may be in the air.

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Original NASA ASRS Text

Title: An Air Carrier was questioned by ATC regarding a descent. Another company aircraft with a similar four digit flight number was on the frequency also on the descent.

Narrative: We were at cruise at FL260 on the Big Sur 2 arrival near PRB headed to SFO. Big Sur VOR was the next fix on the arrival that we were flying to. I was the non-flying pilot handling the radios and monitoring my First Officer (FO) who was flying the aircraft. We were assigned by ATC to descend to FL200. I read back the descent clearance to FL200 and our call sign. There was no read back from ATC that we had the wrong clearance and my FO initiated a descent to FL200. A few moments later ATC asked us if we were maintaining FL260. I told the Controller; no; that we were descending to FL200 as instructed. He told us the descent was for another aircraft and that we were to maintain FL240. We were slightly below FL240 so my FO quickly dialed in FL240 in the altitude alerter and put the aircraft into a vertical speed climb. We captured and maintained FL240 and very shortly there after ATC then issued a new clearance; a pilot's discretion descent to FL200. I believe the Controller told us later that the descent was for another company aircraft. I'm not sure where the mistake was made whether we took another aircraft's clearance or if ATC got confused. The call signs became a problem again when we got on NCT and were being vectored for spacing into SFO. I believe our company was ahead of us on the arrival and the Approach Controller got confused with our call signs. There was again confusion on a heading change assigned to one of us; a 260 heading to 360 if I remember correctly.I believe the event occurred because we do not have a program that identifies similar sounding call signs. Our company should take a hard look at flight numbers that are similar operating in the same geographic location. It's one thing to have an aircraft flying on the West coast and a similar call sign flying on the East. But when there are similar numbers jumbled slightly differently; both flying into the same hub at the same time; problems can occur.Suggestions: Obviously vigilance and a sharp ear is key; but I find it somewhat annoying that we have such similar sounding call signs flying near each other. The program of adding an alphabetical letter to a number which is nothing like the flight number is not working and has its own set of problems. In my opinion; that program should go too. There has to be a simple software program that can analyze assigned flight numbers in geographic areas and identify similar sounding call signs. If not that; then let's drop either the first or last number off the flight number. [There are] two reasons I say to do it that way: 1) because it is similar enough that we as crew still associate it to the flight we are actually flying. Many of us clip our trip sheet to the yoke or somewhere else in the cockpit and reference it as we identify incoming calls or transmit to ATC. We fly many flights a day and unfortunately can't memorize each flight number for every segment. Also the flight number we input into ACARS is the number as designated by the company. We can change it after the fact; but then that can cause confusion in ACARS. 2) To keep our brains on the same page it can be difficult to recall two different flight numbers; one to recite to the passengers; Operations; gate agents; etc. and the other to ATC. If our company really wants to add a letter to the end of a call sign I would recommend adding it to some segment of the flight number. That way we keep some part of the flight number and can distinguish it from other similar call signs that may be in the air.

Data retrieved from NASA's ASRS site as of April 2012 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.