The US Customs & Border Patrol (CBP) has published the guidance on customs procedures related to the four month suspension of tariffs related to the Boeing/Airbus dispute. As a reference, the links are provided below for both the UK and EU tariffs.
United Kingdom – United States
Effective date: March 4, 2021 12:01 AM Eastern to July 4, 2021 12:01 AM Eastern
CSMS #46561075 Notice here
European Union – United States
Effective date: March 11, 2021 12:01 AM Eastern to July 11, 2021 12:01 AM Eastern
CSMS #46590066 Notice here
As mentioned previously, it is encouraging that these tariffs will be suspended at a time when global freight is in such disruption and costs are increasing in supply chains. However NASA is still working with industry coalitions to lend support and urge both the US and EU to come to an agreement to permanently eliminate not only these retaliatory tariffs linked to the aircraft dispute, but also the EU retaliatory tariffs on American whiskey connected to the steel and aluminum trade policies.