It has the potential to bring down more planes.
It didn't bring down the Moroccan plane. Russian president is flying too,
as well as many other delegations. You can fly on a low attitude below
the ash cloud (like the Moroccans did) or use choppers, trains or cars.
Some countries are justified (USA, Canada, Mexico) because they couldn't
fly in small jets or arrive on land, but for the overwhelming majority it is
just a sorry, puny excuse.
Someone has put it beautifully:
we were separated, by the cloud of volcanic ash, from all our false friends.