Paul Chambers of Doncaster lost his appeal Thursday when a judge ordered him to pay $4,800 in costs and fines, The New York Times reported.
In January, grounded in an airport by a snowstorm, he tweeted, "Robin Hood Airport is closed. You've got a week to get your [expletive] together, otherwise I'm blowing the airport sky high!!"
Chambers was convicted of sending a "menacing message" over a public telecommunications network and later was fired from two jobs.
Twitter enthusiasts have offered to pay his legal bills. At #IAmSpartacus, people have expressed their solidarity by reposting Chambers' message and threatening to blow up other things.
"I think I'll blow up Parliament," one wrote. "Oh, wait, that was a JOKE."
"The authorities don't seem to understand the way Twitter works," said Padraig Reidy, news editor of Index on Censorship. "There's no provision in the law for people being hyperbolic, sarcastic or ironic. For a country that prides itself on its sense of irony, that is unfortunate."