He was about to take control of a Rome to Japan flight but was substituted at the 11th hour, with passengers left unaware of the switch.
The incident, which has only now been revealed, happened in January, two months before Andreas Lubitz killed 149 people when he deliberately crashed his Germanwings jet while suffering mental health problems.
The Italian pilot, who is in his 40s but has not been identified, was already known to police after his wife reported him for mistreatment, it was reported by The Times which cited local media.
He threatened to take his own life when his wife initially said she was leaving him.
But when she refused to change her mind, he texted her to say that he was going to crash his plane with 200 people on board that night.
She immediately contacted police whoalerted airport officials.
The pilot, from Padua, Italy, was suspended and is still undergoing psychiatric tests.
The Italian pilots’ union, Anpac, said another incident also happened three years ago when an Alitalia pilot was suspended after his wife raised the alarm.
But he has now been reinstated on the condition that he undergoes various checks.
Lubitz, a 27-year-old co-pilot, deliberately crashed the Germanwings jet en route from Barcelona to Duesseldorf on March 24 last year, killing all 150 people on board.
He locked his captain out of the cockpit before nosediving into the French Alps.
After the crash, it was revealed that he suffered from depression and that the airline knew about his condition.