Depends
From an ownership perspective there are 2 issues.
1. KLM and AF are 2 separate operating companies therefore divorcing the two is straightforward in ownership terms and very clear. As long as assets are clearly demarked, i.e. aircraft.
2. Where problems arise is at the operational level where there are multiple links, inter-twined systems. Novation of contracts is lots of fun, and that's just one line item.
There is also a major accounting issue which seems to get forgotten, Dutch tax treatment of companies is far more favourable than French, therefore Groupe Air France has loaded liabilities on the French side understating the value of what AF brings to the table, and conversely overstating KLM.
This needs to be taken into account when considering fair value of each part of the business.