Air carrier in line for departure at iad on runway 1R understood 'line up and wait' when the clearan...

Narrative:

After being third in line for runway 1R we made it to number 1. After an aircraft landed; I (first officer) thought I heard; 'air carrier X line up and wait 1R.' I replied; 'air carrier X line up and wait 1R;' and the captain started to taxi into position. I then heard an unknown aircraft transmit; 'air carrier X answered that.' tower then replied; 'air carrier X clear runway 1R at K18 and call ground to get back in line.' tower then transmitted; 'air carrier Y heavy line up and wait 19L;' and subsequently cleared him for takeoff. Ground told us; 'no harm no foul;' about our miscommunication. Shortly thereafter; we took off and completed our leg. I obviously heard what I wanted to hear and assumed we were next for takeoff; not realizing an aircraft would be taking off opposite direction from the advertised runway.

Original NASA ASRS Text

Title: Air Carrier in line for departure at IAD on Runway 1R understood 'Line Up and Wait' when the clearance was issued to a same company aircraft at the opposite end of the runway.

Narrative: After being third in line for Runway 1R we made it to number 1. After an aircraft landed; I (First Officer) thought I heard; 'Air Carrier X line up and wait 1R.' I replied; 'Air Carrier X line up and wait 1R;' and the Captain started to taxi into position. I then heard an unknown aircraft transmit; 'Air Carrier X answered that.' Tower then replied; 'Air Carrier X clear Runway 1R at K18 and call Ground to get back in line.' Tower then transmitted; 'Air Carrier Y Heavy line up and wait 19L;' and subsequently cleared him for takeoff. Ground told us; 'no harm no foul;' about our miscommunication. Shortly thereafter; we took off and completed our leg. I obviously heard what I wanted to hear and assumed we were next for takeoff; not realizing an aircraft would be taking off opposite direction from the advertised runway.

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.

Attributes
ACN	933089
Time
Date	201102
Local Time Of Day	1201-1800
Place
Locale Reference	IAD.Airport
State Reference	DC
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Flight Plan	IFR
Person 1
Function	Pilot Not Flying
Experience	Flight Crew Last 90 Days 210 Flight Crew Total 10500 Flight Crew Type 3800
Person 2
Function	Pilot Flying Captain
Events
Anomaly	Conflict Ground Conflict Less Severe Deviation - Procedural Clearance Ground Incursion Runway

Air carrier in line for departure at iad on runway 1R understood 'line up and wait' when the clearance was issued to a same company aircraft at the opposite end of the runway.