Before revision: For example, it is an element of the United States Next Generation Air Transportation System (NextGen), the Single European Sky ATM Research project (SESAR), and India ’ s Aviation System Block Upgrade (ASBU).
After revision: For example, it is an element of the United States Next Generation Air Transportation System (NextGen), the Single European Sky ATM Research project (SESAR), and India ' s Aviation System Block Upgrade (ASBU).