Task: Text to Code
Input (English): Step 1: find the Airline of airlines table for which Abbreviation equals CVO.
Step 2: For each row in airlines table, find the corresponding rows in airports table.
Step 3: find Airline of the results of step 2 whose AirportName equals APG.
Step 4: show the rows that are in the results of step 1 but not in the results of step 3
Output (English): SELECT T1.Airline FROM airlines AS T1 WHERE T1.Abbreviation = "CVO" EXCEPT SELECT T1.Airline FROM airlines AS T1 JOIN airports AS T2 WHERE T2.AirportName = "APG"