At one point in my career, I was working on maintenance software for the US Air Force's C-130 Cargo plane. Floppies weren't used to update the flight software (

At one point in my career, I was working on maintenance software for the US Air Force's C-130 Cargo plane. Floppies weren't used to update the flight software (the Mission Computers didn't have floppy drives). A ruggedized portable computer was used to load the Mission Computer software over a wire connection. The software doing the loading was held to the same MIL-Spec standards as the flight software itself, and we spent a lot of time convincing the reviewers that the checksums used to verify the integrity of the load were sufficient to the task. If the software doing the load is performing its integrity checks to a sufficiently high standard, then I don't see why using a 3.5" floppy disk would be a problem.