Security officials have foiled an attempt to smuggle 80 kilograms of heroin from Islamabad to the West Midlands.
The class A drug, estimated to be worth approximately £2m, was discovered in the luggage of a Pakistani passenger who was travelling to Birmingham.
His suitcases had been cleared by customs but he aroused the suspicion of airport security officials.
Security official Ahmad Khan said the drugs were found in the passenger's suitcase on Thursday.
He said it was believed to be the biggest ever haul of heroin uncovered at the airport, although larger amounts have been found on Pakistan's overland smuggling routes crossing the borders from the poppy fields of Afghanistan.
The drugs were found in plastic bags in three suitcases.
Mr Khan said an investigation was under way to find out how the bags got through customs and the man had been detained.