Federal aviation regulators said Tuesday they are proposing a $1.45 million civil penalty against Northwest Airlines for operating nearly three dozen of its Boeing 757 planes without proper windshield wiring inspections.
A Federal Aviation Administration "airworthiness directive" for Boeing 757s requires inspections - and replacements if needed - for small wires in the heating system for both the captain and first officer's windows, the FAA said.
"Left uncorrected, the problem could cause overheating, smoking and possibly a fire," the FAA said. The directive was enacted in 1990.
Northwest Airlines' maintenance instructions for its mechanics did not include the directive for the first officer's window, the FAA said.
"As a result, 32 of the carrier's 757s flew more than 90,000 passenger flights between December 1, 2005, and May 27, 2008, while not in compliance with the airworthiness directive."
Northwest discovered the problem in May 2008 and revised its maintenance instructions, the FAA said. "However, the instructions did not require the work be performed before further flight, but at the next planned overnight layover."
As a result, the FAA said, 29 of the 32 planes flew while they were still "out of compliance" with the directive.
- CNN's Mike M. Ahlers contributed to this report.