Most likely weren't checked since the planes left the factory yes.
To quote from: https://theaircurrent.com/feed/dispatches/united-finds-loose...
"The five aircraft were delivered to United between November 2022 and September 2023, according to ch-aviation, and would likely not have been through a heavy maintenance C check that occurs every 4,000 to 6,000 hours or two to three years."
Most likely weren't checked since the planes left the factory yes.
To quote from: https://theaircurrent.com/feed/dispatches/united-finds-loose...
"The five aircraft were delivered to United between November 2022 and September 2023, according to ch-aviation, and would likely not have been through a heavy maintenance C check that occurs every 4,000 to 6,000 hours or two to three years."