it is prohibited by LAW to board anyone in the cockpit, disobeyed rule, less knowledge of new airplane ended up killing all passengers on board.
Flight 593 The aircraft involved in the accident was a leased Airbus A310-304, registration F-OGQS, serial number 596, that was delivered new to Aeroflot on 11 December 1992.
Powered by two General Electric CF6-80C2A2 engines, the airframe had its maiden flight as F-WWCS on 11 September 1991 and was one of five operating for Russian Airlines, an autonomous division of Aeroflot – Russian International Airlines that was set up for serving routes to the Russian Far East and Southeast Asia. On average, the crew of three operating the aircraft had logged 900 hours on the type.
Aeroflot Flight 593 was a Moscow–Hong Kong passenger service operated by Aeroflot – Russian International Airlines, flown with an Airbus A310-300, that crashed into a hillside of the Kuznetsk Alatau mountain range, Kemerovo Oblast, Russia, on 23 March 1994. All 63 passengers and 12 crew members perished in the accident.
No evidence of a technical malfunction was found. Cockpit voice and flight data recorders revealed the presence of the pilot’s 12-year-old daughter and 16-year-old son on the flight deck.
One of the children had unknowingly disabled the A310 autopilot’s control of the aircraft‘s ailerons while seated at the controls. The aircraft had then rolled into a steep bank and near-vertical dive from which the pilots were unable to regain control.
The pilot is known to be the only person in history to move in this much of G force. he finally made it to the cockpit but it was too late, no survivors were found.
Disasters don’t just happen it is a chain of events. you can watch the full documentary here