Steve Purvinas, rejected the notion that the incident was sabotage.
It was his union's engineer members who spotted damage to an entertainment system wiring loom as it was being fitted, he said.
"It happened last week when some wires were found to be damaged in a wiring loom that was being fitted to a new [entertainment] system," Mr Purvinas said.
"The most likely situation is that these wires were damaged during manufacturing.
"It was actually members of ours who picked it up - and reported it," he said.
The wiring looms normally come preassembled, Mr Purvinas said.
"It was during the fitment of those looms that our members noticed that some wires were damaged.
"It's quite often that when we're installing new wires in aircraft that looms are too short, or that pins have been put the wrong way around.
"Any suggestion that it was sabotage from our members is clearly another attack by an airline that is leaking information to the press on purpose to take the heat off them for their actions [in grounding the airline] on the weekend," Mr Purvinas said.
