A memorial service for the victims of the crashed Germanwings plane will be held at Cologne Cathedral on Friday.

The service will gather relatives of the victims and the congregation is expected to number 1500 people, the BBC reports.

German Chancellor Angela Merkel and President Joachim Gauck will attend and it is expected that the transport ministers of France and Spain as well as the chief of Lufthansa will also be present.

A candle for each of the 150 victims has been placed on the altar and flags will fly at half-mast across Germany.

The bereaved relatives will be invited to lay flowers on the staircase leading to the cathedral and large screens have been provided for the crowds that will gather outside.

The service will be led by the Archbishop of Cologne and the President of the Protestant Church of Westphalia.

The Airbus A320 was conducting flight 4U 9525 from Barcelona to Dusseldorf, when it crashed in the French Alps on March 24, killing all 144 passengers and six crew members on board.

The co-pilot Andreas Lubitz has been accused of locking the captain out of the cockpit and deliberately initiating the descent of the plane.

Investigators uncovered that Lubitz had a history of depression, which had caused an interruption to his flight training, and was receiving treatment from neurologists and psychiatrists.

It also emerged that doctors had issued him sick notes on several occasions, including on the day of the flight.