SIOUX FALLS, SD -- Raven Industries said sales at its Aerostar division, which includes its contract assembly services, fell 18.4% year-over-year in the April quarter.

Lower contract manufacturing revenue accounted for more than the full decline in revenue. The company reported Aerostar's revenue was $17.7 million as contract manufacturing sales dipped $5.8 million from a year ago, offset in part by $1.4 million in new revenue from Google.

Operating income for the unit was flat, versus a profit of $1.8 million a year ago.

In a move to improve margins, the company is shifting away from contract work toward proprietary product lines.