The Qantas Boeing 737-800 'RetroRoo' is notable for more than just its funky 1970s livery – it's also the last of 75 Boeing 737-800s on the airline's order book, leaving Qantas to ponder a next-gen replacement for its domestic workhorse in the form of the Boeing 737 MAX or the Airbus A320neo.

"At some point over the next few years we'll have to consider what's next" Qantas chief financial officer Gareth Evans told Australian Business Traveller on the sidelines of the RetroRoo's delivery ceremony in Seattle.

Qantas enjoys a relatively young 737-800 fleet – "our oldest 737-800 is 2002 vintage, so it's just middle age" Evan says – "but from a medium- to long-term perspective the next major decision for our domestic fleet is the 737 MAX or A320neo."

Both the Boeing 737 MAX (below) and Airbus A320neo use high-efficiency engines with refined aerodynamics such as new wingtip designs to deliver fuel savings estimated at 13-15%,  along with lower operating costs and reduced noise.

Virgin Australia has already made its call in favour of the Boeing 737 MAX, and has in fact brought forward the first delivery of 23 jets to 2018, while Air New Zealand has chosen the A320neo to sharpen the Kiwi carrier's competitive edge against Qantas on the trans-Tasman market.

Read: Virgin Australia brings forward Boeing 737 MAX: first flights in 2018

"For Qantas we have to evaluate over the next couple of years what's the right aircraft for domestic routes – is it the Neo or the MAX?" ponders Evans. "They're both good aircraft, they're the next step in terms of efficiency, particularly around fuel burn of the engines."

Jetstar has already inked an order for 99 of the A320neo jets from 2016, although Qantas has not ruled out drafting some of the fuel-efficient aircraft into its own red-tail domestic fleet.

For now, following the late December retirement of its last Boeing 767-300, Qantas will enjoy a simplified domestic fleet comprising of the Boeing 737-800 and Airbus A330-200.

While the A330s will mainly feature on transcontinental flights from Sydney, Melbourne and Brisbane to Perth, they'll also be seen more often on east coast routes such as Sydney-Melbourne where they will fill in for the 767-300.

"We will predominately have the A330-200s flying east-west but at the beginning and end of the day they will do some east coast 'triangle' sectors and then they will go on to Perth" Evans says.

This will let some east coast commuters spend those short flights luxuriating in lie-flat beds as the A330s are upgraded with the new Qantas Business Suite.

David Flynn visited Seattle as a guest of Qantas and Boeing.

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