Maintenance at Southwest Airlines is again under investigation by the US FAA.

The agency has confirmed an investigation is underway, but explains it cannot comment while the examination continues. A report in the Dallas Morning News indicates the probe is focusing on fuselage repairs carried out at a repair station in the Seattle area.

Southwest has experienced two highly publicised maintenance investigations during the last two years. The first instance in 2008 occurred after the discovery that Southwest operated 46 Boeing 737s on 59,761 flights after the carrier missed fuselage inspections required under an airworthiness directive issued in September 2004.

In 2009 unapproved parts were discovered on 82 of Southwest's 737s.

Source: Air Transport Intelligence news