Portuguese investigators have launched an inquiry after a severe birdstrike apparently resulted in the cargo door being opened on an Airbus A320.
The SATA International twinjet (CS-TKJ) encountered a flock of seagulls after departing Runway 05 at Madeira bound for Copenhagen.
"Several birds collided with it, hitting engines, fuselage, wing and landing gear," the Portuguese investigation agency GPIAA said.
"At same time, high vibration was sensed and engine vibration indication increased to maximum, in both engines, but no significant power loss occurred."
The aircraft returned to Madeira and carried out an overweight landing on the departure runway, touching down with a landing weight of 68.1t against the maximum figure of 64.5t.
"Landing was uneventful and the aircraft taxied to the ramp by its own means," GPIAA said.
However, it added: "During taxi the control tower informed crew that the forward cargo door was opened, which was confirmed by correspondent warnings in the cockpit."
Initial inspection showed "heavy" impact deformation to fan blades in both CFM International CFM56 engines, although borescope examination indicated no internal damage.
None of the 105 passengers or seven crew were injured in the 20 June event.