Spanish construction group Ferrovial has offered just over 12.5 billion euros for the UK airports’ operator BAA.
It has taken its bid directly to investors after BAA’s board rejected the amount as too low.
Analysts said this appears to be an opening gambit and they expect a higher bid.
Ferrovial is Spain’s second-biggest builder, with revenue last year of 6.9 billion euros.
BAA, with revenue of 2.9 billion euros, operates seven UK airports, three of them serving London.
It also has an interest in Hungary’s biggest airport and others in the US.
Ferrovial is seeking new investments using the money made from a boom in Spanish construction.
It is looking to expand into businesses with faster growth and steadier returns.
BAA has grown as the number of passengers using UK airports almost doubled in a decade.