Boeing reimbursed the US government $4 million after three company mechanics damaged the oxygen system for a VC-25A, a modified VIP 747-200 also known as Air Force One, the US Air Force says in a new accident investigation report.

The VC-25A was damaged as three mechanics checked for leaks in the oxygen system, according to a summary of the Accident Investigation Board report released on 9 May.

Boeing’s mechanics used parts and a cleaning solution that did not meet the cleanliness standards for the oxygen system. An attempt to sanitise the contaminated parts with the unapproved cleaning solution also didn’t follow procedures, the report concludes.

The air force prohibits using contaminated parts in the oxygen system to prevent fires.

The cost to sterilize and re-check the oxygen system added $4 million to the repair bill for the VC-25A, but Boeing has re-imbursed the government for the costs. The damages occurred during a visit to the San Antonio depot from 1 to 16 April last year.

The San Antonio facility inherited the high-profile VC-25A depot contract after Boeing in 2014 closed a decades-old plant in Wichita, Kansas, as part of a cost-cutting, consolidation drive within the Defense and Space business. The site has also completed a 787-8 that was later modified as a Head of State transport for the Mexican government. It also is responsible for maintaining the global fleet of C-17s enrolled in the USAF’s Globemaster III Sustainment Programme.

A year later, the USAF selected the Boeing 747-8 without a competition as the next platform to serve the presidential transport mission, replacing the two VC-25As now in the fleet in 2024.

One month before his inauguration, President Donald Trump criticized the deal for 747-8s as too expensive, but relented two months later after claiming that Boeing lowered its prices.