Creo Interactive Surface Design (Style) > Curves > Editing Curves > To Make a Curve Planar Between Its End Points
  
To Make a Curve Planar Between Its End Points
1. In the Model Tree, right-click the Style feature that contains the free curve, and choose Edit Definition. The Style tab opens.
2. Select one or more free curves.
3. Click Style > Curve Edit. The Curve Edit tab opens.
4. Right-click the selected curve and choose Planar on Endpoints from the shortcut menu.
5. Click .