TRAVERSE CITY — Don't panic if you see a helicopter in the next few days, even if it's flying very low or hovering over a power line.

It's just a crew performing the twice-a-year chore of inspecting some of the thousands of miles of electric power lines that crisscross the state.

ITC Holdings Corp., the nation's largest independent electricity transmission company, is based in Novi. It owns and operates two subsidiaries in the state: ITCTransmission and Michigan Electric Transmission Company, LLC. The two systems operate about 8,700 miles of transmission lines in the Lower Peninsula.

The companies now are conducting semi-annual aerial patrols of high-voltage transmission towers and lines. The flights began in southeast Michigan on May 28. Inspection crews are expected to fly in northern Michigan between about June 21 and 25, weather permitting.

Cherry Capital Airport Director Kevin Klein said the inspection flights typically are not a concern for airport traffic.

"The pilots are very professional, the work very well with the FAA and the air traffic control tower," said Klein. "They're very aware. They do a lot of special coordination ... to avoid the traffic at the airport, and to avoid the obstructions in and around the airport."

The inspection flights generally keep the ITC aircraft well below the flight paths of both commercial and private flights, he said, so normal traffic remains unaffected.

The helicopters might or might not land in Traverse City.

"They could refuel here at the airport, but it just all depends on what their route is," Klein said. "There are multiple general aviation airports in the area they could also fuel at."

The northern Michigan inspections will cover all or parts of Alcona, Alpena, Antrim, Arenac, Bay, Benzie, Charlevoix, Cheboygan, Clare, Crawford, Emmet, Gladwin, Grand Traverse, Iosco, Kalkaska, Lake, Leelanau, Manistee, Mason, Midland, Missaukee, Montmorency, Ogemaw, Osceola, Oscoda, Otsego, Presque Isle, Roscommon and Wexford counties.

The patrols are a North American Electrical Reliability Corporation (NERC) requirement for ITC's vegetation management program. They also help the company stay on top of routine maintenance chores. The patrols include inspections of steel towers, wood poles, wires, insulators and other equipment. Crews check for damaged or worn equipment and vegetation hazards.

The inspection flights often are conducted at low altitudes to allow accurate visual inspection of equipment for lightning damage, wear or other potential problems. A release from the company states this is normal procedure, so there's no cause for alarm if a low-flying helicopter is sighted near transmission lines.

ITC is a subsidiary of Fortis Inc. More information is available at www.itc-holdings.com.