The police Eurocopter crashed into the Clutha Vaults pub in Glasgow, killing nine people on Friday, November 29.
The AAIB is investigating the cause of the crash.
Investigators have found no initial evidence of engine or gearbox failure in their probe.
In a special bulletin, the AAIB said "all significant components were present" at the time the two-engined Eurocopter EC135 helicopter crashed through the roof of The Clutha Bar.
The report went on: "Initial assessment provided no evidence of major mechanical disruption of either engine and indicated that the main rotor gearbox was capable of providing drive from the No 2 engine turbine to the main rotor and to the fenestron drive shaft."
The pilot of the helicopter David Traill, 51, and his two passengers - police officers Kirsty Nelis, 36, and Tony Collins, 43 - were killed in the crash as were six people inside the pub.
The AAIB report today said that the helicopter had left Glasgow City Heliport at 8.45pm on the Friday of the crash and had flown, to start with, to a location on the south side of Glasgow city centre, staying there for about 30 minutes at a height of 1000ft above sea level.
In had then gone about 40 miles east to Dalkeith in Midlothian, staying there for a further 10 minutes before returning to Glasgow.