LONDON — Ash spewing from an Icelandic volcano is bringing disruption and days of uncertainty to more parts of Europe, as officials in Germany said dozens of flights will be grounded today.

Even though some say it’s been a massive overreaction by badly prepared safety regulators – one airline even claims the official scientific findings are simply wrong – hundreds of flights were canceled Tuesday as winds blew the cloud of ash from the Grimsvotn volcano over Scotland and other parts of Europe. Experts say that particles in the ash could stall jet engines and sandblast planes’ windows.

The only comfort for frustrated passengers and airlines is that officials in Iceland said the amount of ash being released by the volcano is decreasing, and officials don’t expect the disruption to be as bad as last year, when millions were stranded after the eruption of Iceland’s Eyjafjallajokull volcano.

Travelers trying to go to or leave Scotland have been hit hardest, but the problem also began to affect Germany, where weather officials said it would not allow any takeoffs or landings at the northern Bremen and Hamburg airports early today due to increased levels of ash in the atmosphere.

Dozens of domestic and international flights were to be affected by the closure early today.