Ryanair chief executive Michael O'Leary said Europe's largest budget airline was canceling all of its flights to and from Britain, Ireland, Belgium, Denmark, Finland, Norway, Sweden, the Netherlands, northern France, northern Germany, Poland and the Baltic states until 1200GMT Monday.
O'Leary cited Ryanair's on-line booking systems, combined with a mounting bureaucratic load for handling refunds and rebookings, as the reason why.
"We hope that by canceling all Ryanair flights over these affected countries ... we can give passengers as much notice as possible to allow them to apply for refunds or rebook alternative Ryanair flights later next week," O'Leary said.
He said too many thwarted passengers since Thursday have been trying to rebook on next-day flights, "only to find that those rebooked flights are then canceled as a result of this continuing volcanic ash problem."
O'Leary said he hoped that, by Monday, "either the prevailing winds will have changed direction or the ash cloud will have dispersed sufficiently to allow flights to operate safely across Ireland, the United Kingdom, Scandinavia and the northern European coastline."
Ryanair's services in southern and central Europe are operating normally, but Britain and Ireland are its two major bases.
Ireland's other major airline, Aer Lingus, announced it was canceling all of its European flights through midday Saturday but its transatlantic services to several U.S. cities would continue. The volcanic ash has yet to appear west of Ireland.