LONDON – A dense ash cloud from an Icelandic volcano blew toward Scotland on Monday, causing airlines to cancel flights, forcing President Obama to shorten a visit to Ireland, and raising fears of a repeat of last year’s huge travel disruptions in Europe that stranded millions of passengers.

Britain’s Civil Aviation Authority said it appears that ash from the Grimsvotn volcano could reach Scottish airspace as early as Tuesday and affect other parts of the U.K. and Ireland later in the week.

British Airways suspended all its flights for Tuesday morning between London and Scotland, while Dutch carrier KLM and Easyjet canceled flights to and from Scotland and northern England at the same time. Two domestic airlines also announced flight disruptions.

But authorities don’t expect the massive grounding of flights that followed last year’s eruption of the Eyjafjallajokull volcano in Iceland because systems and procedures have been improved since then and the cloud is not expected to move over continental Europe.

Pilots unions, however, expressed concerns that the ash could still be dangerous.

Obama, who had been scheduled to spend Monday night in Ireland, was forced to fly to London early because of the ash cloud. Last year’s Icelandic eruption also forced a change in his schedule then, causing him to cancel a trip to Poland.

Glasgow-based regional airline Loganair canceled 36 flights scheduled for Tuesday morning. Another small airline, Eastern Airways, based in northern England, also canceled all flights to and from Scotland on Tuesday.