The train operator's chief executive Andrew Lezala said copper thieves had prevented Metro from meeting its service delivery targets.

He said the low-noise helicopter, which costs $20,000 every time it is launched, had a heat sensitive and night vision camera and could survey around 12 kilometres of the network at any time.

"We could be hovering in Moonee Ponds and looking at people tampering with the railway at Roxburgh Park," he said.

Copper thieves struck 41 times last year compared to 15 incidents in 2011. There have already been 12 incidents this year which has affected 61 train services and 30,000 commuters.

"We have actually managed to continue our punctuality targets over the last few months but we are struggling on delivery in terms of cancellations...we would have met all of our targets had we not had this."

Mr Lezala said Metro spent around $200,000 on repairs every time the thieves stole cable.

Transport minister Terry Mulder said copper theft caused havoc across the network.

"To the commuters who are travelling on the trains, basically all they hear is that there has been a signal failure or a problem with the network, when actual fact is someone has stolen copper wire and upset the signalling system."

Mr Mulder said the Werribee, Craigieburn, Upfield had been the worst affected.

The theft is driven by the global price of copper, which can fetch $7 a kilo. But Metro said the thieves were only collecting a few hundred dollars worth of cable.

The helicopter has already patrolled the network twice, and recently caught people stealing diesel.

A $50,000 reward will be offered to people who provide police with information about copper thieves that leads to a conviction.