Passengers on a Jetstar flight from Melbourne to Perth were forced to move seats during the trip so their off-balance plane could land safely.
The incident occurred on 29 October and is now the subject of an Australian Transport Safety Bureau (ATSB) investigation.
During takeoff from Melbourne, the crew noticed the plane was "nose-heavy" as they attempted to get the Airbus A-321 off the ground.
The pilot said it was necessary to pull back almost completely on the controls in order to lift the nose off the runway.
After takeoff, flight attendants were asked to count the passengers and report back on their seating locations.
After entering the data into their flight management computer, the pilots realised they should not have taken off because there were too many passengers seated towards the front.
"Passengers were relocated within the aircraft cabin to return the aircraft to within allowable limits for the remainder of the flight and landing," the ATSB said.
Head of Aviation at the University of NSW, Professor Jason Middleton, said it was essential that any aircraft was correctly balanced.
"If the aircraft is loaded too far forward, then the control surface isn't enough for the pilot to actually lift the nose up," Professor Middleton said.
"You don't want to have all your heavy rugby league types up the front and all your dancers up the back, or vice versa."