Thanks everybody for clarifying that for me! I see a straight side-to-side fly is impossible.
Another approach:
How about a probe or ship that was orbiting around the planet and made a soft entry in the atmosphere (in a similar way space shuttles do re-entry) and then it went flying spirals around the planet upper atmosphere, going deeper and deeper with each pass...
How long would the ship survive as it enters more dense layers of gas?
Could it go deep enough into the gas planet (even if it can’t reach too close to the core) as to collect data about the composition of the gas and other environmental conditions?
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