It forced the cancelation of hundreds of flights, but Iberia reported minimum impact on services.

The IAG-owned carrier said in a statement that operations began normally at 7 a.m. local time.

It further said only 17% of those involved took part in the strike.

Iberia had warned some airports were likely to be affected, including Barcelona, Bilbao and Malaga.

They added Iberia, Iberia Express and Air Nostrum had cancelled 400 flights, while other IAG partner airlines called off 300 more.

The Iberia representative for the CCOO union, said earlier that it expected the strike to be observed at all airports, including Madrid.

Ground staff are protesting against contracts signed with new providers at Spanish airports.

Spain's commercial airports are operated by state-controlled Aena.

In September, it hired new contractors for services previously provided by Iberia in many airports.

The move upset unions even though the new suppliers committed to retain workers and their working conditions.

Iberia is challenging the new contracts in the Spanish courts, and called strike action "irresponsible".