What are the Single European Sky (SES) and Functional Airspace Blocks (FABs)?
SES = Single European Sky Legal Framework. It started in 2004 when the EU Parliament and Council adopted Reg 549/2004 (framework regulation), 550/2004 , 551/2004 and 552/2004 (interoperability regulation). Also, a very important regulation was 219 which established EASA! (All these legislation is called SES I... amendments later came in place along a myriad of Implementing Regulations) which dealt mainly with What and How the Air Navigation Providers (ANSPs) must provide ANS services. This legislation aims at Uniting the National FIRs (Flight Information Regions) into BIGGER FIRs (Called FABs - Functional Airspace Blocks). Most of the operational advantages of FABs: Direct Routes, lower CO2 emissions and lower fuel burns for air companies are True and EU citizens will gain overall.

Since FABs will include the airspace of more sovereign nations, from a legal point of view, FABs need to be created with a Multilateral Agreement in the adjacent States.