The train was en route Thursday from Spirit AeroSystems Holdings Inc. in Wichita, Kan., when it derailed near Rivulet, Mont., about 50 miles west of Missoula.
The 19 rail cars involved in the derailment were also carrying assemblies for the 777 and the 747 jumbo jet, but they have been inspected and "their content appears undamaged," Boeing said. The company is continuing to assess damage to six 737 fuselages that tumbled from the train, and how that will affect production.
A white-water rafting firm snapped photos of three cracked 737 fuselages sitting down an embankment that runs along the Clark Fork River.
"Once we determine the extent of damage we will assess what, if any, impact there will be to production," said Lawrence Wilson, Boeing spokesman for supplier management.
The 737 is a short- to medium-range airplane that has been in service since 1968. There have been several versions of the aircraft over the years — the latest have list prices of $76 million to $110 million.
To keep up with demand growing 737 demand, the Chicago company recently increased production to 42 a month at its facilities.
Spirit AeroSystems in Wichita builds fuselage sections for all current Boeing programs.
A 737 fuselage section is placed on two rail cars in Kansas City for the trip to Boeing's lines in Washington for final assembly, according to rail officials.
Montana Rail Link, which was responsible for the train at the time of the accident, said that the speed limit where the train derailed was 35 mph.
The train was traveling 31 mph, said Lynda Frost, a rail link spokeswoman.
"The cause of derailment is still being assessed," she said, adding that there have been 953 Boeing cars on Montana Rail Link from June 2013 through 2014.
Crews had extracted one fuselage from the river Sunday with plans to remove a second one by end of Monday, Frost said. The third was to be taken out Tuesday.
While cause of the derailment is under investigation, the 777 and 747 assemblies will be shipped to Washington and arrive over the next several days, Boeing said. Alternate rail routes are available for future shipments.
In Monday trading, Boeing's stock rose 58 cents to $129.09.