Both the message and the timing of the first public appearance by a member of Lubitz's close family since the 2015 disaster that claimed 150 lives have been criticised by victims' families, who will be holding their own anniversary events to mark the tragedy.
German prosecutors in January closed their investigation after concluding that Lubitz, 27, was suicidal and bore sole responsibility for the catastrophe.
Now his father, 63-year-old Günter Lubitz, will present his own findings to reporters alongside journalist Tim van Beveren, whom he called “an internationally recognised aerospace expert”.
“Up to now, everyone has believed the theory of a co-pilot who was depressed for a long time, who deliberately crashed his plane into a mountain in a planned act. We are convinced this is false,” the father said in a press release.
The daily Frankfurter Allgemeine Zeitung said that the two men would present the theory of a carbon monoxide leak in the cabin which disabled the co-pilot, who was alone at the controls at the time of the crash.
'A very responsible person'
Lubitz senior told news weekly Die Zeit that the image of the suicidal loner or cold-blooded killer did not correspond with the man he knew.
“Our son was a very responsible person. He had no reason to plan and carry out a suicide, and certainly not to take another 149 innocent people with him,” he said.
He accused investigators of gross negligence, and called for a new probe.
“There were very clearly things that weren't even looked into, perhaps because they didn't want to look into them,” he said.
Lubitz insisted he was simply seeking answers “just like the other relatives who lost a loved one”.
Elmar Giemulla, a lawyer representing several of the victims' families, said this week that Lubitz was waging an “irresponsible” campaign that would be rip open old wounds.
“I imagine that Mr Lubitz wants to promote a theory that would absolve his son of any responsibility,” Giemulla told the Rheinische Post newspaper.
Prosecutor Christoph Kumpa, whose office led the German investigation, also dismissed Lubitz's accusations.
“There are no indications of a cause of the crash that is not linked to deliberate — presumably suicidal — behaviour,” he told DPA news agency.
Lubitz's parents had already angered the families last year when they placed a heartfelt newspaper advert in their son's memory to mark the first anniversary of the crash.
Entitled simply “Andreas” and featuring a smiling photograph of the co-pilot, the brief text ended with a message to their son in bold letters: “We miss you very much but you are and will remain in our hearts”.
They spoke of a year “filled with horror and fear” but did not explicitly mention the 149 other people killed in the crash.
Meanwhile the victims' families will devote the anniversary on Friday to remembering their loved ones.
Five hundred people are expected to travel to the French Alpine town of Digne-les-Bains for an ecumenical church service.
Later in the nearby village of Vernet, where the unidentified human remains from the disaster are buried, a memorial will be inaugurated before some relatives continue on the crash site.
And in the western German town of Haltern am See, which lost 16 students and two teachers who were returning from an exchange programme in Spain, their school will hold a commemorative ceremony.
Its principal, Ulrich Wessel, expressed disbelief about Lubitz's planned press conference.
“There are various ways to deal with grief – perhaps also different ways to perceive reality, or not perceive it,” he told public broadcaster SWR.