Germanwings co-pilot Andreas Lubitz may have spiked his flight captain’s coffee with a diuretic that made him need to go to the toilet.

Lubitz, 27, made internet searches for diuretic drugs before he crashed the Airbus 320 into the French Alps on March 24 - killing all 150 people on board, Express.de reports.

Investigators are believed to have found the information on Lubitz’s laptop but are yet to comment on the information publicly.

Lubitz is believed to have locked 36-year-old captain Patrick Sondheimer out of the cockpit after he went to the toilet and refused to let him back in.

Diuretics increase the need to urinate and may have hastened a trip to the bathroom by Mr Sondheimer.

Lubitz’s laptop also reportedly shows that he searched for ways to kill himself just 24 hours before the crash.

The co-pilot was taking medicines for depression, anxiety disorders and panic attacks and allegedly lied to doctors about being on sick leave.

Meanwhile there have been growing calls for the heroic efforts Mr Sondheimer made to try to avert the crash to be recognised.

Data from the flight’s voice recorder reportedly showed Mr Sondheimer frantically tried to smash his way back into the cockpit as he shouted at Lubitz: "For God's sake, open the door”.

Mr Sondheimer was a father-of-two who was only working on the doomed flight because he had changed his roster to work shorter haul flights so he could spend more time with his family.