Air passengers have been urged to regularly check their airline websites for updates amid fears of further transport chaos in the coming days after a huge volcanic ash cloud continued to blow south from Iceland yesterday.

As both Ryanair and Aer Lingus cancelled flights to Spain and Portugal yesterday, with some transatlantic flights also cancelled, the Irish Aviation Authority (IAA) said the cloud is currently approximately 1,000 miles long and 800 miles wide.

The volcanic ash cloud has now taken a crescent shape around Ireland and any change to the prevailing weather conditions could bring the concentrated ash back over the country.

Airports were closed or due to close across northern Spain and Portugal and parts of southern France yesterday, with Spanish authorities confirming that 15 northern airports would close until at least 4pm due to high concentrations of ash.

But although Irish airspace continued to be clear of volcanic ash – with airports expected to remain open until at least midnight yesterday – the IAA warned the ash cloud situated over the north Atlantic is drifting over the Iberian peninsula, and other parts of southern Europe, posing a risk to flights in those areas. Parts of the UK may also be affected.

"North Atlantic flights and flights to/from southern Europe may be impacted over the weekend," it said. "Airspace over northern Scotland may also be at risk later today. Passengers should regularly check their airline websites for up-to-date information in this regard."

Aer Lingus cancelled two flights from Dublin via Shannon to Boston, but moved to accommodate passengers on later flights.

It was also forced to cancel all bar two of its flights from Dublin, Cork, Belfast and Gatwick to Spain, Portugal and the Canary Islands for the remainder of the day.

"The outlook for the remainder of the day is that there is uncertainty over the operation of flights from Ireland to the south of France," it added.

Meanwhile, Ryanair also cancelled 13 flights to southern Europe, affecting destinations such as Alicante, Faro, Malaga and Seville.

Met Éireann said the volcanic plume was expected to "hold" off the Irish west coast into early today.

"However, the fact that significant quantities of ash have been thrown very high into the atmosphere may pose some logistical problems for transatlantic flights, which will have to be routed either above or around this high-level ash plume," it warned.

"Later Sunday and on Monday the ash cloud may return to Irish air space as surface winds become more northeast to north and the upper-level winds are north to northwest."