On 21 March 2018, Houthi rebels released a video where they hit and possibly shot down a Saudi F-15 in Saada province.
Viganò resigned on 21 March 2018.
On 21 March 2018, 19 arrests were made in Rome of alleged members belonging to the Licciardi clan of the Camorra and members of the Filippone 'ndrina and Gallico 'ndrina accused of drug trafficking.
On 21 March 2018, Castellón beat the record of seasonal tickets in the fourth-tier division with 12,701, and is considered a giant amongst minnows.
On 21 March 2018, the Central Committee of the Communist Party of China unveiled a reform plan for the People's Armed Police Force.
The vessel returned to Canada on 21 March 2018 spending 197 days at sea, the longest deployment by a Victoria-class submarine in Canadian service.
On 21 March 2018, Stam resigned as manager after a 9-game winless run.
On 21 March 2018, it was announced that Citigroup changed its policy to forbid its business customers from performing certain firearm-related transactions.
Highlights of the challenge were broadcast in a one-off documentary, airing on 21 March 2018 on BBC One.
On 21 March 2018, Packer resigned as executive chairman of Crown Resorts.
A multistorey hotel fire occurred in the building containing the Metro Hotel Dublin and two floors of apartments, on 21 March 2018.
On 21 March 2018, it was announced that each ship would have their two diesel engines replaced by three new ones at Cammell Laird in Birkenhead as part of the "Power Improvement Project" (PIP).
On 21 March 2018, Houthi rebels released a video allegedly showing a RSAF F-15 being hit in Saada province by a R-27 air to air missile adapted for surface to air use.
On 21 March 2018, Kosovo's Assembly ratified the border agreement with Montenegro.