The accident involved an employee of Inflite Engineering Services and an agency worker, who were carrying out checks to the tail of an aeroplane, Chelmsford Magistrates' Court was told.
The two men were standing on MEWPs either side of the plane's tail when another worker closed the wrong circuit breaker, inadvertently opening the air brakes (used to increase drag or the angle of approach during landing) and knocking over both platforms.
One man sustained a punctured lung, a broken back and ribs, and fractures to his pelvis and elbow. The second broke his wrist and chipped a bone in his back.
The Health and Safety Executive (HSE) found the company had not carried out a suitable risk assessment and there was a lack of effective monitoring.
Inflite Engineering pleaded guilty to breaching ss 2(1) and 3(1) of the Health and Safety at Work Act on 15 March. It was fined and ordered to pay costs of almost £5,500.
HSE inspector Tania van Rixtel said after the hearing: "Both of these men suffered shocking injuries after falling from height, which could easily have been a double fatality. Our investigation found the incident could have been avoided had adequate monitoring been taking place."