Aegean Airlines, the former island-hopper that's expanded to replace defunct Greek flag-carrier Olympic Air, plans to order at least 50 new single-aisle jetliners in the next three or four weeks.

Aegean, which has already doubled its fleet since 2013, will choose between the latest Airbus SE A320neo and Boeing Co. 737 Max narrow-body models, Chief Executive Officer Dimitrios Gerogiannis said in an interview Wednesday.

"We are now in the last mile of the process, really in the last days," Gerogiannis said at the Aviation Club in London.

The aircraft, to be delivered between 2020 and 2024, will replace an aging all-Airbus jet fleet, as well as add capacity for expansion, according to Gerogiannis. Aegean said it'll probably need 75 planes by 2023, a figure that includes turboprop models to link Athens with domestic locations.

A baseline A320neo jet has a list price of US$110.6 million, valuing Aegean's planned deal at at least US$5.5 billion. While the carrier currently owns only four of its Airbus planes, leasing the rest, that proportion may increase with the new fleet, Gerogiannis said. The company may also take a higher number of bigger narrow-bodies than it has now to help meet growth plans.

Aegean was founded as a regional carrier in 1999 and traded blows with Olympic after the state operator was privatized in 2010. The Greek economic crisis weakened the larger company and Aegean won approval to step in and take it over in 2013, transforming into a major international airline.

Gerogiannis said there's no immediate prospect of Aegean entering the long-haul market on routes once served by Olympic, though that's something that may be considered going into next decade. Shares of the company have gained 9 percent this year after advancing 30 percent in 2017, valuing it at EUR 643 million(US$790 million).