Pensioner Jean-Louis Lioret, who was flying to Bangkok from Paris on Etihad Airways, was arrested after cabin crew overheard him using the word bomb in an exchange with his co-passenger, his brother Michel Lioret said.
During a stopover at Abu Dhabi, Lioret's neighbour asked him to keep a packet on the other seat next to him as it was empty.
Lioret's jocular "I hope it's not a bomb" was overheard and sent off alarm bells.
He was taken off the plane and grilled by police and then jailed. He was also informed that the packet contained cigarettes and not a bomb.
The French foreign ministry said it was informed of the arrest and was following the case closely.