The father of one of the victims of this week's plane crash in the French Alps has called for airlines to take greater care over pilots' welfare.

French prosecutors have said they believe German co-pilot Andreas Lubitz deliberately slammed the Germanwings flight into a mountain.

Authorities have since said Lubitz hid evidence of an illness from his employers - including a sick note for the day of the crash.

"I believe the airlines should be more transparent and our finest pilots looked after properly," said Philip Bramley, from Hull. "We put our lives and our children's lives in their hands."

His 28-year-old son, Paul Bramley, was one of 150 people killed in Tuesday's disaster.

Speaking near the site of the crash, Philip Bramley said Lubitz's motive was irrelevant.

"What is relevant, is that it should never happen again; my son and everyone on that plane should not be forgotten, ever," he said.

German prosecutors, who have been trying to determine what caused Lubitz to take such a devastating decision, met their French counterparts today to discuss the preliminary findings of their investigation.

Dusseldorf prosecutors say Lubitz hid evidence of an illness from his employers - including a torn-up doctor's note that would have kept him off work the day authorities say he crashed Flight 9525.

Searches conducted at Lubitz's homes in Dusseldorf and in the town of Montabaur turned up documents pointing to "an existing illness and appropriate medical treatment", but no suicide note was found, said Ralf Herrenbrueck, of the Dusseldorf prosecutors' office.

Prosecutors did not specify what illness Lubitz may have been suffering from, or say whether it was mental or physical. German media reported that the 27-year-old had suffered from depression. The New York Times and Germany's Bild am Sonntag weekly also reported that Lubitz had eye problems.

Dusseldorf University Hospital said yesterday that Lubitz had been a patient there over the past two months and last went in for a "diagnostic evaluation" on March 10. It declined to provide details, but denied reports it had treated Lubitz for depression.

Colleagues and acquaintances described Lubitz as an affable man in good physical health who was focused on a career as a pilot.

Frank Woiton, another Germanwings pilot, said Lubitz told him he wanted to become a long-distance pilot and fly Airbus A380 or Boeing 747 planes.

Mr Woiton, who like Lubitz comes from Montabaur, said he met Lubitz for the first time three weeks ago when they flew Dusseldorf to Vienna and back together.

Mr Woiton told German public broadcaster WDR yesterday that Lubitz did not stand out and appeared like any other colleague. Lubitz "flew well and knew how to handle the plane", he said.

Lubitz also frequented a gliding club near the crash site as a child with his parents, according to Francis Kefer, a member of the club in the town of Sisteron.

Mr Kefer told i-Tele television that Lubitz's family and other members of the gliding club in his hometown of Montabaur came to the region regularly between 1996 and 2003.

The crash site is about 30 miles (50km) away from the Aero-club de Sisteron glider airfield.

Officials at the club would not comment.

The area, with its numerous peaks and valleys and stunning panoramas, is popular with glider pilots. In the final moments of the Germanwings flight, Lubitz overflew the major turning points for gliders in the region, flying from one peak to another, according to local glider pilots.

A special Mass was held today in the nearby town of Digne-les-Bains to honour the victims and support their families.

The plane shattered into thousands of pieces, and police are toiling to retrieve the remains of the victims and the aircraft from a hard-to-reach Alpine valley near the village of Le Vernet.

Following the crash, the European Aviation Safety Agency (EASA) issued a new recommendation that all airlines in Europe should require two people in the cockpit at all times during flight.

If one of the pilots leaves the cockpit - only allowed during the cruising stage - then a flight attendant needs to take his or her place.

Ilias Maragakis, a spokesman for the agency, said EASA's recommendation is not binding but airlines generally follow them. Once the crash investigation has been completed, the agency may review and amend its compulsory regulations and requirements.

Questions have been raised about what airlines should do to ensure their pilots are fit to fly.

Germanwings, the Lufthansa subsidiary that Lubitz joined in 2013, declined today to comment when asked whether the company was aware of any psychological problems he might have had. But it said he had passed all required medical check-ups.

Aviation experts say those checks are stringent but focus mainly on physical health. A pilot's mental state is usually only assessed before companies decide whether to admit them to a training programme - and even then a determined person could hide a latent problem.

David Hasse, the editor-in-chief of German aviation website airliners.de, said: "The test that will get you into a Lufthansa flight training program is a very hard test and this is why most people who get into those pilot classes will train for those tests."

"There are coaching facilities, companies that are specialised in training people on how to pass those tests, and they will also advise you on how to behave in the psychological tests."