BOGOTA Colombia's flag-carrier airline Avianca will invest $473 million to grow its fleet by 16 aircraft as it looks to increase the number of routes on offer, Chief Executive Adrian Neuhauser said on Thursday.

Avianca will lease 14 Airbus A320 NEO planes and two A320 CEO planes to push its daily flights on domestic routes up by almost 25%, from 600 to 750.

Neuhaser during a press conference in Colombia's Bogota called the increase of almost 1 million weekly seats "unprecedented growth" in the airline's history.

"The resources to finance the incorporation of these planes come from our available cash and additional debt that we take on leases," Neuhaser said.

The 16 planes will join Avianca's fleet between October and the end of December, the executive said.

Avianca's employee head count will grow by some 1,200, Neuhaser added.

Some of the new hires will come from Viva Air, a now-defunct Colombian budget carrier Avianca had sought to buy before it backed out of the deal, citing conditions imposed by Colombia's civil aviation regulator.

(Reporting by Luis Jaime Acosta; Writing by Oliver Griffin; Editing by Mark Porter)