Three weeks after a prominent member called the size of the F-35 joint programme office (JPO) “disturbing”, the Senate Armed Services Committee has proposed to disband the organisation just as an $8 billion follow-on modernisation programme is taking shape.

The committee’s version of the National Defense Authorisation Act for Fiscal 2017 approved on 16 May would eliminate the JPO after the Lockheed Martin fighter transitions to full rate production two years later. Management responsibilities would be divided by variant, with the US Air Force taking over procurement and modernisation of the F-35A and the US Navy gaining the same powers over the F-35C and the Marine Corps’ F-35B.

If adopted by the full Senate and the House of Representatives and signed into law by President Barack Obama, the provision would mark the single-largest change in the management of the programme since it was formed in the late-1990s to manage the fly-off between the Lockheed X-35 and Boeing X-32. It would also raise questions about the status of international partners under the new management structure.

The Senate committee wants the programme to be managed directly by the services that operate the aircraft, rather than under a joint office that reports directly to the offices of the Secretary of Defense.

“Despite aspirations for a joint aircraft, the F-35A, F-35B, and F-35C are essentially three distinct aircraft, with significantly different missions and capability requirements. Devolving this programme to the services will help ensure the proper alignment of responsibility and accountability the F-35 program needs and has too often lacked,” the committee wrote in a summary of the bill.

The passage echoes criticisms raised during a 26 April committee hearing focused on the F-35 programme, when Arizona Senator John McCain called on Lt. Gen. Christopher Bogdan to describe the staff and budget under his command. McCain disagreed with Bogdan’s reply that the office comprised 2,590 workers with a $70 million annual budget, saying he understood the office employed nearly 3,000 with a $300 million budget. But he called even the $70 million yearly budget for a single acquisition office “disturbing”.

The F-35 is entering a critical transition period from a development phase with low-rate production to operational status with full-rate production. The USMC has already activated its first F-35B squadron in Yuma, Arizona, with limited capabilities. The USAF plans to follow suit with the first F-35A squadron reaching initial operational capability (IOC) in August, although Bogdan admits a critical back-end system for managing spare parts and logistics will not be ready until October.

At the same time, the JPO has started planning a controversial follow-on modernization programme, aiming to convert the F-35’s software-based avionics applications to open architecture standards and to upgrade the aircraft’s sensors and weapons with technology developed since the aircraft’s design was frozen in 2004. McCain has opposed the Pentagon’s plan to have the JPO manage the so-called Block 4 upgrade as an extension of the existing programme. Instead, he prefers that the estimated $8 billion upgrade package be managed as a separate programme, with a competitive acquisition and a fixed-price development contract.