There was a close partnership between LY and DL. I think you were able to collect miles on all scheduled flights use miles etc on DL and vice versa for LY. This partnership ended at the end of the Wintertimetable in March when DL introduced it's non stop JFK-TLV flights. LY has a new partner now, it's AA not sure if you can collect miles and use them on all AA flights or only on specific routes.