They also must take into account that moving electrical lines underground makes routine maintenance of the system more difficult, and thus more expensive.
In the previous alarming incident, a maintenance worker discovered an electrical fire aboard an empty Japan Airlines 787 slated for departure from Logan International Airport in Boston on January 7.
The company, which provided mechanical and electrical services such as air conditioning, boiler maintenance and heating installation, said it was closing with immediate effect because of the current economic climate.
Bridge operator's Forth Estuary Transport Authority (Feta) maintenance workers have installed several miles of ductwork to accommodate electrical wiring.