A F/A-18C Hornet fighter jet of the Swiss Air Force is pictured during a presentation at the airbase in Payerne, Switzerland March 27, 2017. REUTERS/Denis Balibouse

ZURICH (Reuters) - Switzerland could eventually be in the market for as many as 70 new fighter jets or as few as 20 under scenarios laid out on Tuesday by a defense ministry task force examining how to replace the neutral country’s aging air force fleet.

The most expensive and powerful option would be to buy 55-70 aircraft and ground-based air defense weapons for an estimated 15 billion to 18 billion Swiss francs ($15.3-$18.4 billion), according to the report.

It did not say which aircraft the government should consider.

The least expensive option would be procuring 20 jets and accompanying ground-based air defense systems for 5 billion francs. Other options called for buying 40 or 30 new aircraft plus surface-to-air defense support.

Switzerland is looking to replace its fleet of Boeing McDonnell Douglas F/A-18C and D Hornets and outdated Northrop F-5 Tigers, all of which are scheduled to be retired in the 2020s.

The cheapest option would mean keeping the F/A-18s in service longer than planned, the panel said.

It suggested the government decide by 2020 what kind of jets to buy and to finance the deal via the regular defense budget.

That would help avoid the risk of having to subject the purchase to a popular referendum under the Swiss system of direct democracy. Voters in 2014 shot down plans to buy 22 Gripen E fighters made by Swedish company Saab AB.