MISSOULA, Mont. — Boeing is deciding what to do with six newly manufactured commercial airplane bodies that fell off a train in a derailment in Montana, including three that slid down a steep riverbank, a company spokeswoman said Monday.Experts from Boeing Co. and Spirit AeroSystems, which built the fuselages, are at the site of Thursday’s derailment on the Clark Fork River about 50 miles west of Missoula, spokeswoman Dina Weiss said in a statement.“Once we have completed our assessment of damages and determined our next course of action, we will decide what to do with the fuselages,” she said.She said in a statement that other Boeing 777 and 747 airplane parts on some of the 19 cars that went off the tracks appear undamaged and will be shipped to the company’s Everett, Wash., assembly plant.The derailment sent three 737 fuselages down an embankment of the Clark Fork River and knocked three others from the train. Weiss said it was not immediately clear whether they were 737-700s, which are relatively short at 110 feet from nose to tail, or the longer 737-800s or 737-900s, which are more than 133 feet long.The fuselages were being shipped from the Spirit AeroSystems plant in Wichita, Kansas, to a Boeing facility in Renton, Wash., to be assembled into airliners. They originated on a BNSF Railway train, but switched to Montana Rail Link to travel through southern Montana, where the derailment occurred, said Gus Melonas, a spokesman for Fort Worth-based BNSF. The huge blue-green fuselages are a common site on railways along the 2,000-mile trek from Kansas to Washington state. Ken Evans, senior manager for Spirit AeroSystems, said the company ships 42 of the 737 fuselages each month.Spirit AeroSystems has been designing, building and shipping the fuselages by rail from Wichita since 1968, he said.“In my memory, we’ve not had a serious derailment like this before,” he said Monday.Crews with heavy equipment were working to hoist the fuselages from the river. Montana Rail Link spokeswoman Lynda Frost has said it could take until Tuesday.The toppled hulls have become a spectacle for rafters to gawk at as they float past the partially submerged hulls on the Clark Fork River. Staff writer Steve Kaskovich contributed to this report.