Two men, aged 30 and 41, have been removed from the aircraft and taken to a police station for questioning, Essex Police said.
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The first Blue Moon since 2012 will appear over the UK on Friday. The next won't be until 2018.
Other hate crimes against muslims and gay people have also risen.
Archie's mum was fed up with the balloon floating around her living room so suggested he let it go to see how far it could travel.