* Official says ash could hurt military capability
* NATO says Afghan operations not affected
* Disruption underscores importance of Afghan transit deals
* NATO ministers’ meeting in doubt due to flight bans (Adds Rasmussen, paragraphs 8-9)
By David Brunnstrom
BRUSSELS, April 19 (Reuters) - Glass build-up from Iceland’s volcanic eruption has been found in an engine of a NATO F-16 fighter plane, a U.S. official said on Monday, underlining the dangers to aircraft of flying through the ash cloud.
The official did not say which nation’s aircraft had been affected, where it happened or when, but it was the second air force to report problems from the ash cloud — Finland, not a NATO member, reported similar problems on Friday.
The volcanic ash consists of tiny particles of rock and glass as fine as talcum powder, which under extreme heat can fuse onto the blades of an engine, causing imbalances or damaging delicate rotating machine parts.
“Allied F-16s were flying and they did find glass build-up,” the U.S. official said, adding that the glass had been found in the engine of one plane that had flown in European airspace.
“So this is a very, very serious matter that in the not too distant future will start having real impact on military capabilities ... if the ... issue doesn’t disappear.”
The official said the ash cloud had already led to the scaling down of some U.S. military exercises. Planes were still flying in these, “but it is dangerous”, he said.
“I think the airspace is closed for a reason,” the official added, referring to flight bans that have affected much of Europe for the past five days.
NATO Secretary-General Anders Fogh Rasmussen nevertheless told a news conference there had been no negative effect on alliance operations, including its main mission in Afghanistan, nor on the alliance’s own defence.
“Our air forces will always take the necessary steps to ensure they are capable to conduct their operations. They have taken the necessary steps and they will take the necessary steps to ensure our territorial defence is secure,” he said.
Finland’s Defence Forces said on Friday they had conducted flying tests with F-18 Hornets in Lapland, and even during a short test time it was possible for the ash to cause “significant” damage to the plane’s engines.
They said they studied an engine from one of the planes with a fibreoptic camera, and saw the extreme heat had caused the ash to melt, raising the risk of blockages and possible overheating.
They said that this, in turn, could lead to moving parts cracking and, at worst, breaking off and destroying the engine.
Airline industry group IATA has criticised Europe’s response to the ash cloud and called on Monday for urgent steps to reopen airspace after closures costing airlines $250 million a day.
Dutch airline KLM, which has flown several test flights, said most European airspace was safe despite the plume of ash, and sent two commercial freight flights to Asia on Sunday.
The U.S. official said he expected NATO to discuss the imapct of the ash cloud and said it underscored the importance of deals with Russia and Kazakhstan for transit of troops and supplies to Afghanistan.
“It opens up the possibility of the polar route for lethal equipment and troops to be shipped into Afghanistan which is exceedingly important given the force buildup we have.”
Officials said the ash cloud had raised doubts about whether a meeting of the 28 NATO foreign ministers scheduled on Thursday and Friday in Estonia and due to be attended by U.S. Secretary of State Hillary Clinton could take place.
“She is in the U.S. and has to get here, and it’s too late to take a boat,” the U.S. official said. (Additional reporting by Brett Young in Helsinki; editing by Tim Pearce)