Plans were recently submitted to the Queenstown Lakes District Council to build two 18m high hangars in six stages.
Museum curator Jason Rhodes hopes the application will be considered by an independent commissioner without the need for public notification.
A notification determination hearing to decide whether there will be a full hearing has yet to be scheduled.
Key to the development is the decision to put half of the building underground, requiring massive earthworks of some 120,000cu m.
That would meet the council's 9m building height restriction in the rural general zone.
The buildings would not appear to be any larger than those already on the site, Mr Rhodes told the Otago Daily Times.
"We hope to use the groundfill as much as possible for landscaping, roading and concrete," Mr Rhodes said.
The Wanaka Transport and Toy Museum is the largest private collection open to the public in the southern hemisphere.
It was founded over 50 years ago by Mr Rhodes' father, Gerald, of Christchurch, who worked for International Harvester and later established a car and truck wrecking business.
Gerald Rhodes chose the airport site to house his collection in 1988 because the dry Central Otago climate was suitable for preserving machinery.
The first building was constructed in 1994.
A second building, known as "The Hangar", was finished in 1995 and the museum opened to the public in December 1995.
In April 2004, a 1440sq m building called "The Fire Station" was completed and by December 2005 the 2000sq m "Hangar 2" had been added to the site.
In the new plans, Hangar 2 would be extended in four stages with a large internal atrium surrounded by five mezzanine floors allowing the public to look down on items on the bottom floor.
A second display building would be built alongside it in two stages.
When completed, the proposed development would provide four times the space used now to display exhibits.
The Rhodes collection includes New Zealand's largest public toy display as well as a variety of vehicles, planes and motorbikes.
Many of the vehicles have gone through a restoration programme.
Most of the exhibits, which number more than 300,000, were sourced from within New Zealand, particularly the South Island.
The collection has been financed by the owner and gate receipts.
Annual visitor numbers are between 20,000 and 21,000, Mr Rhodes said.
"This is the endgame for everything . . . We have the feeling we are doing something a national museum would never do. It is all about retaining the small things in life that are disappearing," Mr Rhodes said.
