Narrative:

High and late for descent into day caused by ATC; on the verge of requesting lower; ATC issued an immediate descent; minimum of 2000 feet per minute from FL280 to FL240. Both the pilot monitoring (pm) and I heard air carrier X; the pm read back the clearance. Then ATC directed air carrier X to turn 10 deg left for traffic; almost immediately we received a traffic alert. Then ATC asked what altitude air carrier X was at. The pm replied passing FL260 for FL240 at 2000 ft per min. The ATC controller sounding confused; directed continued left turn for traffic; and asked another aircraft what their descent clearance was? They replied FL280 for FL240 at 2000 ft per min. I believed everyone realized what happened; and ATC admitted that two [company] aircraft with similar sounding flight numbers; answered the same clearance; the read back from both aircraft was blocked; and ATC admitted heard neither; nor notified both aircraft that similar sounding flight numbers are on the same frequency. ATC then stated 'no harm; no foul'!! Both aircraft were going to day; and we; landed well ahead of the other aircraft.similar sounding flight numbers; on the same frequency; in the same proximity; plagues [our company]; again!!! ATC not notifying said aircraft of this hazard. Ps. The next controller warned both aircraft of similar sounding flight numbers; the controller at the time of the event did not.it's been said; [our company] was going to change policy to minimize similar sounding flight numbers being dispatched in close proximity in time; and space to minimize this hazard. It seems to be getting worse; I've had multiple situations of similar flight numbers in recent weeks.

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Original NASA ASRS Text

Title: Air carrier flight crew reported an airborne conflict due to similar call signs and a communication breakdown with ATC.

Narrative: High and late for descent into DAY caused by ATC; on the verge of requesting lower; ATC issued an immediate descent; minimum of 2000 feet per minute from FL280 to FL240. Both the Pilot Monitoring (PM) and I heard Air Carrier X; the PM read back the clearance. Then ATC directed Air Carrier X to turn 10 deg left for traffic; almost immediately we received a Traffic alert. Then ATC asked what altitude Air Carrier X was at. The PM replied passing FL260 for FL240 at 2000 ft per min. The ATC controller sounding confused; directed continued left turn for traffic; and asked another aircraft what their descent clearance was? They replied FL280 for FL240 at 2000 ft per min. I believed everyone realized what happened; and ATC admitted that two [company] aircraft with similar sounding flight numbers; answered the same clearance; the read back from both aircraft was blocked; and ATC admitted heard neither; nor notified both aircraft that similar sounding flight numbers are on the same frequency. ATC then stated 'no harm; no foul'!! Both aircraft were going to DAY; and we; landed well ahead of the other aircraft.Similar sounding flight numbers; on the same frequency; in the same proximity; plagues [our company]; again!!! ATC not notifying said aircraft of this hazard. PS. The next controller warned both aircraft of similar sounding flight numbers; the controller at the time of the event did not.It's been said; [our company] was going to change policy to minimize similar sounding flight numbers being dispatched in close proximity in time; and space to minimize this hazard. It seems to be getting worse; I've had multiple situations of similar flight numbers in recent weeks.

Data retrieved from NASA's ASRS site 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.