Simplify the following text for a Grade 9 native English-speaking person.
Original: Monarch 's fleet consists of 30 aircraft : 4 Airbus A300 aircraft , 5 Airbus A320 aircraft , 16 Airbus A321 aircraft , 2 Airbus A330 aircraft and 3 Boeing 757 aircraft .
Simplified: In 1993 , Monarch Airlines introduced the first Airbus A320-200 aircraft into its fleet and in 1997 introduced the first Airbus A321-200 into the fleet . The Airbus A320-200s and Airbus A321-200s eventually replaced the airline 's Boeing 737-300s .