In the aircraft.cfg look for ui_wglts=0 and change it to ui_wglts=1

An easy way to do this is to use ctrl+h and in the
Find what: enter ui_wglts=0
and in the
Replace with: enter ui_wglts=1

then click on Find next and click on Replace each time it finds it.

OR: you could just click on Replace all    <--- I tend to use this one mostly. Unless I don't want them all to have the winglets.

Hope this helps

Mark