UPDATE 2-Spain to part-privatise airports, weak price seen

(Recasts, adds minister and analyst comment, detail, background)

By Ben Harding

MADRID, Aug 1 (Reuters) - Spain will privatise some 30 percent of the world's biggest airport authority, AENA, it said on Friday - but juicier investment options abroad and cash-strapped buyers at home would squeeze the price, analysts said.

Under the plan, the government will split air traffic services from airport management, keeping the former in state hands while part-privatising the latter.

Infrastructure Minister Magdalena Alvarez told a news conference that the whole of AENA, which manages 47 airports, was worth 30 billion euros ($46.7 billion).

However, analysts said specialist infrastructure funds would probably be more interested in rival privatisations at Chicago Midway, Prague and St Petersburg, as a Spanish deal would not deliver them majority control.

Meanwhile, at home, many of the obvious buyers -- construction firms -- are staggering under hefty debts and a property slowdown that will force them to drive a hard bargain on price, if they bid at all.

It's awkward timing for a government that is searching for cash to prop up an economy in crisis.

"It's not going to be a crazy price," said BNP Paribas analyst Steven Fernandez.