Iad tower controller and flight crews reported a ground conflict at iad airport. Controller reported...

Attributes
ACN	1578005
Time
Date	201809
Local Time Of Day	1801-2400
Place
Locale Reference	IAD.Airport
State Reference	DC
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Route In Use	None
Flight Plan	IFR
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Conflict Ground Conflict Critical Deviation - Procedural Published Material / Policy

Narrative:

Aircraft X was given line-up and wait on runway 19C and was told multiple aircraft will be crossing the runway down field. I then followed that transmission with a takeoff clearance with aircraft X. Somehow; I did not remember giving a departure clearance to aircraft X and proceeded to cross 2 aircraft across the runway. Those aircraft were aircraft Y and aircraft Z. Aircraft X stated that he was aborting takeoff clearance because aircraft Z was given takeoff instructions. The pilot was correct and extremely professional about the entire situation.I did not recall clearing aircraft X for takeoff. My strip management procedures was correct. The only recommendation I can make is turning the strip over if I am going to be crossing aircraft while having an aircraft in position and hold just slow the situation and force me to [be] extra cautious. We rarely use this operation; but it can be applied all of our operations.

Original NASA ASRS Text

Title: IAD Tower Controller and flight crews reported a ground conflict at IAD airport. Controller reportedly forgot about clearing an aircraft for takeoff and then clearing crossing traffic downfield on the departure runway.

Narrative: Aircraft X was given line-up and wait on Runway 19C and was told multiple aircraft will be crossing the runway down field. I then followed that transmission with a takeoff clearance with Aircraft X. Somehow; I did not remember giving a departure clearance to Aircraft X and proceeded to cross 2 aircraft across the runway. Those aircraft were Aircraft Y and Aircraft Z. Aircraft X stated that he was aborting takeoff clearance because Aircraft Z was given takeoff instructions. The pilot was correct and extremely professional about the entire situation.I did not recall clearing Aircraft X for takeoff. My strip management procedures was correct. The only recommendation I can make is turning the strip over if I am going to be crossing aircraft while having an aircraft in position and hold just slow the situation and force me to [be] extra cautious. We rarely use this operation; but it can be applied all of our operations.

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.

Iad tower controller and flight crews reported a ground conflict at iad airport. Controller reportedly forgot about clearing an aircraft for takeoff and then clearing crossing traffic downfield on the departure runway.