US National Transportation Safety Board engineers have used a home-grown analysis program to narrow the search area for fan blades that separated from the right engine of a Southwest Boeing 737-300 on 17 November.

The Ballistic Trajectory Analysis, developed by the NTSB, takes into account the aircraft's ground track, speed, prevailing winds and other factors to predict an area where the pieces are most likely to be found. Investigators successfully used prediction tools in January 2007 to locate the missing pieces of an America West CRJ200LR's CF34 engine after an uncontained failure at 24,000ft (7,258m) over sparsely populated mountainous terrain in Colorado.

In this case, the program has narrowed the search area for the blades and spinner from an uncontained engine failure to a swathe 0.64km wide and 2.7km long on sparsely populated private property in Hunt County, Texas.

The aircraft was climbing through 25,000ft (7,560m) after take-off from Dallas Love Field on 17 November when the pieces of the CFM56's fan blade and spinner separated from the engine and fell to the ground. The aircraft, with five crew and 133 passengers bound for Little Rock, Arkansas, returned safely to Love Field using the left engine. As well as damage to the engine and its housing, the aircraft sustained "minor" damage to its fuselage.

The NTSB had asked members of the public who may come across the components not to pick them up, but to mark their location. "These engine parts and the exact location of discovery are essential to the investigation," it added.