Complex sentence: The announcement was made almost immediately after Alaska Air Group announced its intention to acquire Virgin America and merge it with Alaska Airlines, and either Alaska or Virgin operated in 4 out of 7 of JetBlue's newly announced markets.
Split into simpler sentences: The announcement was made almost immediately after Alaska Air Group announced its intention to acquire Virgin America and merge it with Alaska Airlines. Either Alaska or Virgin operated in 4 out of 7 of JetBlue's newly announced markets.