Planes to Evacuate 400 U.S. Civilians : Saudi Arabia: The departures are voluntary. About 6,500 others plan to remain in the kingdom.

Four hundred American civilians called the U.S. consul general here Saturday to accept a government offer to evacuate them on military planes from Saudi Arabia’s war-jittery Eastern Province.

Their departure was voluntary, and most of the province’s American community--numbering about 6,500--apparently have decided to weather the war in Saudi Arabia. Washington’s offer to fly out the Americans in the kingdom, at their own expense, applied only to those living in the Eastern Province.

The 750 Americans living in Bahrain also were offered military evacuation. U.S. officials said that more Americans were likely to sign up for the military flights over the rest of the weekend. The date of their departure to an undetermined European destination will depend on the availability of aircraft.

The Saudi oil industry, which has increased its production to an estimated 8.5 million barrels a day since Iraq’s invasion of Kuwait Aug. 2, is heavily dependent on American expertise, and Saudi officials had worried that production would be hampered if the U.S. government ordered the evacuation of its nationals, as several countries have done.

“Basically spirits are pretty good in the American community,” said Jess Arceneaux, principal of the junior high school at the ARAMCO (Saudi Arabia American Oil Co.) complex. “I’ve been getting a lot of calls, but people seem to be calm. I had breakfast this morning at the golf course.”

Despite the lack of panic in either the foreign or Saudi populations here, a somber mood has settled over this Persian Gulf-front city, where one is reminded every moment that the war is only a Scud-missile flight away. The war is one that most Saudi citizens had convinced themselves could be fought and won without their deep involvement and without serious disruption to their lives. They were wrong.

Throughout the day and night, allied attack aircraft--many of them piloted by Saudis--roar through the skies, disappearing behind a plume of fiery exhaust. The roads are clogged with military equipment moving toward the Kuwaiti front, and the streets of nearby Al Khobar, the region’s main shopping district, are strangely quiet.

No mail or international newspapers have reached Saudi Arabia since the war began three days ago. Nor have any scheduled commercial airlines flown in or out of the kingdom since then, because all air space over the region has been designated for military use only.

The causeway to Bahrain, an island-state 45 minutes from here, has been closed by Saudi authorities, effectively cutting the kingdom’s last non-military transportation link to the outside world. Commercial flights to and from Bahrain also have been suspended.

During the first hours of the war, Saudis gathered around television sets tuned to CNN and cheered pictures of the air strikes on Baghdad as though they were rooting for their favorite football team.

But the early giddiness gave way to a feeling of unease after Iraqi gunners fired a Scud missile at Dhahran that a U.S. Patriot anti-missile battery intercepted and destroyed at the edge of the city Friday, creating a huge explosion before dawn.

Now even cab drivers travel with gas masks in the seats next to them and don’t work past midnight. The 24-hour Safeway store has started closing at midnight.

The U.S. Embassy in Bahrain said Saturday that it will provide Americans there with gas masks, something most Americans in the Eastern Province already have.

But in perhaps the most optimistic gesture of the war, the Kuwaiti Information Ministry in Dhahran has begun soliciting journalists to join a trip advertised as “Return to Kuwait.” There are 98 names on the list.