Trump's initial action was to restrict travel to China, not outright ban flights. US citizens and their immediate families were still allowed to fly. Whether this action was "quick" is at least somewhat debatable.

The only outright ban on flights I could find was something from June [0], well after the initial restrictions were put into place, and that was in response to China refusing to allow more flights into China from US carriers. It was also (partially) lifted just a few days later [1].

[0]: https://www.regulations.gov/document/DOT-OST-2020-0052-0014

[1]: https://www.wsj.com/articles/u-s-eases-flight-ban-on-chinese...