The Defence Department renewed a contract Wednesday with a Halifax-based aerospace company to maintain its fleet of Cormorant helicopters.

The seven-year deal with IMP Aerospace is worth $591 million.

IMP Aerospace, a division of IMP Group Ltd., was awarded a seven-year contract in July 2000 to service and provide on-site support for the Cormorants, which operate out of Greenwood, N.S., Comox, B.C., and Gander, N.L..

The military ordered 15 of the search-and-rescue helicopters in 1998 and they entered service in August 2001 — but the fleet has been overshadowed by mechanical concerns and a fatal crash off Nova Scotia last year.

Three crew members were killed and four were injured when a Cormorant crashed into waters off Canso, N.S., on July 13, 2006, during a routine training exercise.

A draft of the final report into the crash has been complete for months, but the military has yet to reveal what they've determined caused the helicopter to go down.

Soon after the helicopters entered service, the military discovered the aircraft required far more maintenance time than originally thought, and mechanical problems were soon reported in the choppers' hoists.

In February 2004, the military suspended training flights after two aircraft developed fuel leaks in the engines, and all but essential and test flights were suspended in October 2004 because of the discovery of dangerous cracks on a tail rotor.

IMP Group Ltd. is a privately held group of companies that employs more than 3,000 people around the world.

The company's customers also include Boeing, Lockheed Martin, Bombardier, Airbus and Bell Helicopter.