According to DRI sources, the narcotic substance was seized from the duo's suitcases in the intervening night of June 22 and 23.
They had concealed the 40 kg heroin in their suitcases among packets of sugar and maida, DRI sources said, adding an airline staffer had helped them in carrying them.
The three, all Indian citizens, have been detained and interrogation was on, they said.
Meanwhile, DRI officials today seized unaccounted US currency, valued around Rs 30 lakh, from a Colombo-bound passenger.