It seems quite a rapid decision by CANSO to resume flights ......I work in a UK University where we have some specialists in this area, with links to staff "on the ground" in Iceland.
It appears that the eruption IS entering 'another phase', but exactly what that is remains to be seen. It should be remembered that when Eyjafjallajökull erupted in 1821, the eruption continued on-and-off until 1823, and this also triggered the 1823 eruption of the neighbouring volcano Katla.
As I understand it, the ash production in the current eruption is due to the fact that the volcano is melting the glacier, causing rapid cooling and fragmenting of the magma.
See this article from Dr David Rothery, of the Department of Earth & Environmental Sciences, at The Open University :
Times Online - Eureka Zone - WBLG: Ash plume shows first signs of dying down
"The reason behind the apparent dying down of the ash production is likely to be that the volcano has been cut off from the supply of meltwater, which has until now been pouring into the volcano vent. When the magma hits the ice and water, it cools down incredibly quickly leading it to shatter into tiny fragments, which shatter into fine ash light enough to be carried high into the atmosphere. The evaporating steam helps power the ash up into the sky.
Volcanologists have been predicting that as walls of solid magma build up around the vent the volcano less melt water will feed into the eruption. It looks as though this could have happened now.
"There is no guarantee that the situation will not revert to what was happening Thursday-Sunday, but there are grounds for cautious optimism," said Dr Rothery"