Originally Posted by Donegal

I am planning to book a Discover Airlines flight within Europe (4Y-operated) in Economy and may want to upgrade to BC with cash payment online later. Now, on Lufthansa.com the flight is offered with the same price once 4Y flight number, once with LH flight number (codeshare). I have heard from friends that in such case it is advisable to book the LH-flight number (in case irreg ops LH would be rebookable to other Star Alliance operators, 4Y would not). But now my question: Does it make it any difference which flight number I book in regards to the later possibility to online-upgrade?