The US plane manufacturer Boeing has begun flying 737 Max jets that were refused by Chinese airline customers back to the United States, as the trade war between the world’s two biggest economies escalates.
Bloomberg reported earlier this week that China had instructed airlines to stop taking delivery of Boeing jets.
No, assuming that they weren’t worked on any further and are being returned as-exported. Even if they weren’t originally US made, you’ve got three years from US export to claim duty relief (assuming you paid the duties when they came into the US first time round).
https://www.cbp.gov/trade/programs-administration/entry-summary/hts-subheading-9801