The Swiss fleet is planned to arrive in the latest “Block 4” configuration, an Armasuisse spokesperson told Swiss agency Keystone-ATS. The reassurance comes despite concerns over the troubled Technology Refresh 3 (TR-3) upgrade, a $1.9 billion programme running three years behind schedule.
The TR-3 package underpins the Block 4 capabilities, which include advanced sensors, new weapons integration and enhanced electronic warfare systems. According to the US Government Accountability Office (GAO), TR-3 delays forced the Pentagon to accept 174 provisionally delivered F-35s in a non-combat-capable configuration.
The GAO reported on 3 September 2025 that all 110 jets delivered in 2024 arrived late, with an average delay of 238 days compared with 61 days in 2023. It further warned that Block 4 is at least five years late, $6 billion over budget, and will initially include fewer capabilities than originally planned.
Armasuisse maintains that the Swiss aircraft will arrive combat-ready and that the current F135 engine will not require replacement. Engine core upgrades and cooling system improvements under the Power and Thermal Management Upgrade are expected only from the mid-2030s.
Political opposition has grown since US President Donald Trump imposed a 39% tariff on Swiss imports on 1 August 2025. Left-wing lawmakers warn the measure could add up to $1.3 billion in extra costs, while government supporters argue cancelling the order would harm Swiss-US trade relations and delay the long-overdue modernisation of the Swiss Air Force.
In early August 2025, Swiss National Armaments Director Urs Loher visited Lockheed Martin’s facilities in Fort Worth for discussions on offset obligations and project monitoring. Armasuisse described the trip as part of routine consultations to track programme progress and clarify industrial cooperation under the F-35 deal.
The first Swiss pilots and maintainers are expected to begin training in the United States ahead of the 2027 handover.
