A controversial new air traffic control system is finally in operation at Delhi airport in India -- nearly two years after out-dated technology was blamed for a serious mid-air collision.

The accident, between a Saudi Airlines Boeing and a Kazakh cargo plane, killed nearly three hundred and fifty people.For the past six months, controllers at Delhi have refused to use the new equipment because they said they couldn't monitor radio conversations with aircraft properly.

However, officials believe the controllers' union was more concerned that the new system is able to assess blame for near-misses which pilots say happen too frequently over India.

The start-up of the new system comes after weeks of disruptions of flights to and from the capital because of thick fog.The new system should enable Delhi airport to operate in virtually all weather conditions.