Why wouldn't the Hungarian delegation make it in? Have you even looked at the path of the ash???
Due to the Jetstream winds it moves east, occasionally south. The entire Scandinavia, the UK and initially many central European countries were affected.
Besides, the Hungarian and Austrian delegations could've driven if they wanted to, not that far away.
First airports that opened up for US lights into Europe were Madrid and Lisbon, again due to their location - the Jetstream takes the ash away from them.
Amazing how there must be a conspiracy in everything nowadays.
Could Obama have flown in? Probably. Land in Madrid and take the train or a motorcade all the way to Poland. Alternatively he could've taken a southern route and flown to Greece, Turkey and taken train or used a motorcade. However, as a head of state his flight would've gotten all kinds of special treatments, additional spacial separation, etc. which means other, regular flights would be delayed even more, possibly past their "slot time" meaning they'd be cancelled. [applies to all "official" head of state flights, in other words the entire airplane consists of a government delegation]
No defender of Obama by no means but the decision to cancel was logical one.I also predict that if Eyjafjallajökull's big sister (brother if you prefer) Katla erupts you'll see many airlines in Europe and maybe in the US too go bankrupt. The strength of that volcano is estimated to be at least 10 times that of Eyjafjallajökull. Airlines will be grounded for weeks - scary stuff!