New Delhi, July 29 (IANS) India Friday signed a $2.4 billion contract with two French defence firms for upgrading its 51 Mirage combat jets that were acquired in the 1980s.

"Thales and Dassault Aviation today signed a contract for the upgrade of the Indian Air Force's Mirage-2000 fleet," a press release from the two French companies said Friday.

A spokesperson for the two companies here said it was a "commercial contract" between the firms and the Indian government.

The Indian defence ministry also confirmed the deal, which the cabinet committee on security had approved a fortnight ago.

"Based on the integration of latest generation equipment and systems, the upgrade will further enhance the technical-operational capabilities of the Indian Air Force's Mirage 2000. The aircraft represents a long tradition of cooperation with French military aviation, initiated 50 years ago," the release from two firms said.

The contract comes even as India's defence ministry and the Indian Air Force top brass remained split over the high cost of upgrading the Mirage-2000 aircraft and the likely benefits to the country's future air power needs.

Taking into account $1 billion for new weapons and another $500 million for new facilities at Bangalore-based Hindustan Aeronautics Limited (HAL) for the upgrade, the cost could rise to close to $4 billion, according to government sources.

Thus, the cost of the upgrade may work out to $79 million per aircraft, which, the opponents of the deal contend, is the same as that of the 126 fighters that India is buying under the $10.4 billion medium multi-role combat aircraft (MMRCA) tender.

Those supporting the deal argue that once upgraded, the aircraft will be as potent as a new combat plane.

Among the upgrades planned for Mirage-2000 are a night vision goggle-compatible glass cockpit, advanced navigational systems, advanced Identification Friend or Foe (IFF) system, advanced multi-mode multi-layered radar, fully integrated electronic warfare suite and advanced beyond visual range (BVR) capability.

The new weapons include 450 MICA interception and aerial combat missiles.

Thales and another French firm, MBDA, will be the weapons systems integrator and missiles supplier respectively.

Two of the planes will be upgraded in France by manufacturer Dassault Aviation, two in India with French help and the remaining 48 entirely by HAL. The upgrade of the entire fleet will take nine years.

The IAF inducted the Mirage-2000 between 1982 and 1986.