At 20.30 hours on 18 Jan 1940 the Patria was spotted on a southerly course by U-9 and was suspicious because no national markings could be seen from the distance of 500 metres. At 22.23 and 22.40 hours, the U-boat fired one torpedo each, but missed with both. 30 minutes later, the Flandria was spotted and sunk with one torpedo at 23.53 hours about 95 miles north of Ymuiden before the Patria was hit underneath the bridge by one torpedo at 01.45 hours on 19 January, which caused the ship to sink rapidly north of Ymuiden.

The survivors from Flandria (Master Albert Emil Rönne) were picked up from a raft by the Norwegian steam merchant Balzac after two days. The master and 16 crew members were lost.