Lufthansa expects to complete its purchase of a 45% stake in Brussels Airlines before the end of June, after the European Commission (EC) sanctioned the deal today.
To allay competition concerns over routes to Brussels, the EC has told Lufthansa to sell certain airport slots to rivals "if a competitor wants to take up that route", says a Lufthansa spokesman.
Up to 10 slots at Frankfurt, Munich, Hamburg and Zurich airports are potentially available.
From 2011 Lufthansa will be allowed to purchase the remaining 55% in Brussels Airlines.
Lufthansa, which still awaits an EC decision on its proposed takeover of Austrian Airlines, says that regulatory clearance for the Brussels deal will "enable both carriers to realise synergies, further strengthen their competitive position and intensify their co-operation".
SN Airholding is the parent company of Brussels Airlines.
Brussels Airlines says: "Harmonised schedules, which will lead to improved connections at the Frankfurt, Munich, Zurich and Brussels hubs, are just one of the advantages that customers can look forward to in future."