Switzerland last fought a foreign war 200 years ago and has no discernable enemies yet wants to spend billions on new fighter jets.
Many oppose the idea, saying the neutral country neither can afford nor needs cutting-edge warplanes to defend Alpine territory which a supersonic jet can cross in 10 minutes.
Critics of the plan state that Ireland, Malta and Luxembourg do not have jets, making the 6 billion Swiss franc ($6.6 billion) plan a waste of money.
"Who is our enemy? Who is attacking a small, neutral country — surrounded by NATO?" asked Priska Seiler Graf, a member of parliament for the left-leaning Social Democrats. "It's really absurd."
Voters get their say on Sunday September 27.
Approving funding in the binding referendum would let the government decide next year among the Eurofighter from Airbus, the Rafale from France's Dassault, Boeing's F/A-18 Super Hornet, or the Lockheed Martin F35-A Lightning II.
The aircraft would replace Switzerland's aging fleet of 30 F/A-18 Hornets which will go out of service in 2030.
Seiler Graf said cheaper alternatives, such as a fighter version of Leonardo's M346 trainer, offered better value than the "expensive toys" under consideration.