TAXI FOR TKOF MOVING FROM BEHIND ANOTHER ACFT; WINGTIP STRIKE.

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ON TAXI OUT AT DCA WE WERE TOLD TO FOLLOW ACR TO RWY 18. WE WERE INSTRUCTED TO KEEP IT TIGHT TO ACR. ACR WENT INTO RUN UP BLOCK POSITIONED #1 FOR TKOF. WE WERE TOLD TO FOLLOW AND 'KEEP IT TIGHT TO ACR IN THE RUN UP BLOCK.' ACR WAS TO OUR LEFT AND SLIGHTLY AHEAD OF US. WE SPENT 10 MINS IN THE RUN UP BLOCK BEHIND ACR. WE WERE THEN TOLD TO TAXI INTO POS AND HOLD ON RWY 18. AS WE TURNED RIGHT TO PASS ACR; MOVING VERY SLOWLY; OUR LEFT WINGTIP CONTACTED THE ACR LGT RIGHT WINGTIP WE STOPPED. THERE WERE NO FLUID LEAKS EVIDENT. WE CALLED RAMP CTL AND TOLD THEM WE HAD MADE CONTACT AND REQUESTED MECHS. WHEN MECHS ARRIVED AND INSPECTED ACFT; THEY HAD ACR PULL FORWARD TO DISENGAGE WINGTIPS. ACR THEN TAXIED BACK TO GATE. WE TAXIED BACK TO GATE BEHIND ACR AND PARKED. TRIP CANCELLED. THERE WERE NO INJURIES TO PEOPLE. THERE WAS NO EVAC. DCA ARPT VERY CONGESTED ON GND AND IN AIR. WE WERE LED TO BELIEVE THAT ACR WOULD BE #1 TO DEPART. RADIO FREQ TOO CONGESTED TO VERIFY TKOF SEQUENCE. TOLD TO KEEP IT TIGHT IN THE RUNUP BLOCK AND DID SO ASSUMING ACR WOULD BE #1 FOR TKOF. CLOSER POS TO ACR ACFT THAN IF WE HAD KNOWN WE WOULD TKOF FIRST. SURPRISED BY CALL INTO POS AND HOLD FOR USE AHEAD OF ACR. VERY HARD TO SEE OUR WINGTIP ON STRETCHED AND LGT. THOUGHT WE HAD WINGTIP CLRNC; WE DID NOT AND MADE CONTACT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: CALLBACK INDICATES FAA HAS SENT LETTER RE INVESTIGATION. COMPANY HAS TAKEN NO ACTION BEYOND CREW REVIEW.