The airline, which flew to 25 cities, said Brexit uncertainty and rises in fuel and carbon costs led to it filing for administration on Saturday.
One Briton stuck in Belgium said the airline would not refund her fare and she could not afford an alternative.
Flybmi's move puts 376 jobs at risk and comes as other airlines face problems.
On Sunday, Loganair stepped in to take over three Flybmi routes from Aberdeen to Bristol, Oslo and Esbjerg. However, these will not start until 4 March.
