Originally Posted by
WineCountryUA
Multiple reports this has been unreliable for the past few years.
I have done this as recently as 3 weeks ago and it worked very well crediting some segments to UA and other to LH ... no problem whatsoever.
YMMV, but w/ different operating carriers and splitting that up should not be an issue. Taking a connecting flight on UA and changing the program at the connecting airport is trickier ... but it can be done.