With plans to modernize its fleet, Cebu Pacific has completed the sale of four of its Airbus A319 planes to low-cost carrier, Allegiant Air.

The Gokongwei-led Cebu Pacific confirmed the said sale on Thursday, with four of its aircrafts scheduled for delivery between 2017 and 2018.

“Cebu Pacific (PSE: CEB), signed a forward sale agreement with a subsidiary of Allegiant Travel Company (NASDAQ: ALGT),” The Philippine low-cost airline said in a statement.

Jude Bricker, Allegiant Travel Company Chief Operating Officer, said that the deal is part of the company’s transition to single fleet type operations.

Cebu Pacific’s Chief Executive Officer and president Lance Y. Gokongwei said that the transaction is in line with its plan to upgrade its fleet with modern aircrafts to prepare for expansion locally and internationally.

“Between 2016 and 2021, we are anticipating the delivery of 30 Airbus A321neos, for long-range capability, and 16 ATR 72-600 turboprop planes, for better inter-island connectivity,” Gokongwei added.

The average age of Cebu Pacific’s fleet is at 4.82 years. The company said that it is one of the youngest fleets in the world. So far, the company has 57-strong fleet that is composed of eight ATR 72-500, six Airbus A330, 36 Airbus A320 and seven A319.

Cebu Pacific is expecting the delivery of 30 brand new Airbus A321neo aircraft, the largest model in the A320neo series. The model could deliver up to 20 percent fuel savings with additional range capability or payload.

To boost its local network, the airline also purchased 16 ATR 72-600 turboprop aircraft.

Cebu Pacific is a low-cost airline in the Philippines based on the grounds of Ninoy Aquino International Airport (NAIA) (Manila Terminal 3). It was founded on Aug. 26, 1988 as Cebu Air. It operates on more than 90 routes on 64 destinations that cover Asia, Middle East, Australia and the U.S.