James Brown, a former Paralympic athlete, was given a 12-month jail sentence on September 24 2021. The cyclist was arrested after supergluing himself to the roof of a British Airways plane at London City Airport on October 10 2019.
On December 8, Mr Brown was released from prison on bail pending a ruling from the Court of Appeal.
On January 14, three appeal judges, Lord Burnett, the Lord Chief Justice, Lord Justice Singh and Mr Justice Goss, ruled the 12-month jail term should be cut to four months.
However, they dismissed his appeal against conviction.
Lawyers representing Mr Brown, blind since birth, claimed when lodging the appeal in December there had been no reason to charge him with causing a public nuisance.
The lawyers argued the sentence was “manifestly disproportionate” and said Brown suffered “unique hardship” in prison due to his disability.
They added he could have been charged with aggravated trespass and claimed custody was not justified on the facts of the case.
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Mr Brown, a double gold medallist from Belfast, live-streamed his protest attempt for an hour while he was on top of the British Airways plane on October 10, 2019.
He climbed onto the aircraft at London City Airport before glueing his right hand to it, then wedged his mobile phone in the door to prevent it from closing.
Southwark Crown Court was told during his trial that 337 passengers saw their flights cancelled, and the disruption cost the airline around £40,000.
It comes as three XR activists were cleared over a 2019 protest which saw them cause 77 minutes of disruption to a central London train.
Reverend Sue Parfitt, 79, Father Martin Newell, 54, and former university lecturer Philip Kingston, 85, were unanimously acquitted by a jury at Inner London Crown Court of obstructing the railway following their protest at Shadwell Station on October 17 2019.
Mr Kingston super-glued his hand to a Docklands Light Railway (DLR) train while Rev Parfitt and Father Newell climbed on the roof and said prayers for the planet, shortly before 7am.
The trio said they were strongly motivated by their Christian faith, while Mr Kingston said the futures of his four grandchildren also prompted him to take part in the protest.