Federal Aviation Administration regulators this week announced they would seek a civil penalty of $10.2 million against Southwest Airlines Co. for flying aircraft that had not been checked for fatigue-related cracking. The penalty would be the largest ever levied by the FAA.Southwest is charged with operating nearly 60,000 flights in 2006 and 2007 using 46 planes that had missed inspections for possible fatigue-related cracking on the fuselage areas, according to the Associated Press. The carrier continued to operate flights with the same aircraft in March 2007 with the knowledge that it had failed to conduct the required inspections. It is these later flights that account for all but $200,000 of the penalty. Southwest acknowledged that six of its planes had small cracks that required repairs, but said it would contest any penalty as it had complied with regulators' requests.A spokeswoman for Southwest insisted that the planes operated by Southwest were safe and that the six aircraft with small cracking were discovered in preventive inspections. Boeing assured Southwest that flying the planes for up to 10 days until they could be inspected again did not pose a risk, according to the spokeswoman.