Overcoming leftist opposition, Parliament formally approved the transfer to an Italian base of 72 American F-16 fighter-bombers that have been ordered out of Spain within three years.

As the debate drew to a close Thursday, members of the Young Communist Federation, militants of the small Proletarian Democracy Party, and peace activists staged a sit-in in a square in front of the Chamber of Deputies.But Prime Minister Ciriaco De Mita's five-party coalition stuck solidly together in the chamber to approve the eventual transfer of the U.S. 401st Tactical Wing to Italy by 298 votes to 196 with 24 abstentions.

A decision on where to redeploy the F-16s, which are capable of carrying nuclear weapons, became necessary after Spain insisted in January that the wing must leave its base at Torrejon, near Madrid, within three years. The F-16s became a national sovereignty issue.

The powerful Italian Communist Party, flanked by other small leftist factions and environmental protection groups, led the opposition to the transfer in the two-day parliamentary debate.

As the Italian Parliament debated the issue Thursday, the U.S. Air Force grounded routine F-16 flights in Europe to review flight safety following the crashes Wednesday of three of the planes in West Germany.

The grounding was to last for two days but will, in effect, last five days because of the weekend and the July 4 holiday.