DUBAI (Reuters) - A small plane crashed south of Dubai airport killing three Britons and one South African, the Dubai Civil Aviation Authority said in a statement on Thursday.

The four-seat plane, a DA42 registered in the United Kingdom, was on a mission to calibrate terrestrial navigation systems at the airport, the statement said.

An investigation is underway. Air traffic at the airport has returned to normal, it said.

Reporting By Ahmed Tolba, writing by Stephen Kalin; Editing by Janet Lawrence