What happens to the employees who could not work due to the volcanic ash cloud?

The Icelandic ash cloud trapped many employees which, without doubt has implications from an Employment Law perspective. Could this be considered as a reason for dismissal? Could it result in the refusal by the employer to pay the salary for the days on which the employee was not providing their services? Article by Diana Rodríguez, published in "El Economista", 3 May.