COLOGNE, Germany — Switzerland’s new defense chief, Viola Amherd, has intervened in the course of the multibillion-dollar “Air 2030” program, tasking a former Swiss astronaut with critiquing its underlying premises.

Claude Nicollier, an astrophysicist and former military pilot, has until the end of April to review a 2017 expert report on the $8 billion project to buy a new fleet of fighter aircraft and ground-based air-defense gear.

The second opinion is expected to delay the political process for the program. Technical evaluations of contractor offerings will proceed as planned this spring and summer, the defense ministry said in a statement.

Former defense chief Guy Parmelin had planned to present a full program and investment plan for Air 2030 to parliament in February. Government officials still want to subject the proposal to a referendum in 2020.

Replacing the country’s decades-old F/A-18 and F-5 jets will eat up the lion’s share of the program, at roughly $6 billion. The rest will go to new, ground-based, air and missile defense weapons.

The envisioned concept of operations dictates that a fleet of 30 or 40 aircraft will intercept those targets outside of the ground weapons’ range. Officials want enough capacity to have four planes in the air at any given time during crises.

Defense ministry spokesman Renato Kalbermatten told Defense News that Nicollier’s scope for critiquing the 2017 expert report is wide open, which means anything from aircraft numbers to cost is open for scrutiny. It is not expected, however, that the review will question the overall need for the program, he said.

Notably, a reassessment of the threats expected to be countered by the modernization program is part of Nicollier’s mandate.

Swiss officials received offers from five aircraft makers on Jan. 25: Airbus with its Eurofighter, Boeing's F/18 Super Hornet, Dassault's Rafale, Lockheed Martin's F-35A and Saab's Gripen E.

In the ground-based interceptor portion of the program, the Eurosam consortium is expected to offer its SAMP/T; Israel’s Rafael is pitching David’s Sling; and Raytheon wants to sell its Patriot system. The three vendors met with Swiss industry representatives earlier this month in preparation for a requirement to offer offset deals worth 100 percent of the eventual contract.

Those deals are meant to benefit a broad section of Swiss industries, including the country’s famed watchmakers, according to Armasuisse, the country’s defense acquisition office.