DHAHRAN, SAUDI ARABIA, JAN. 18 (FRIDAY) -- U.S. commanders have warned American pilots not to be lulled into a sense of complacency over the relative ease of their first bombing runs over Iraq.

"It's not over . . . and we need to be smart about it," warned Lt. Col. Don Kline, commander of the 27th Tactical Fighter Squadron who led one of the first flights of F-15 fighters over Iraq Thursday. "We had one good morning. You sting 'em quick, you're winning 7-0, but . . . you get overconfident and they beat you."

U.S. bombers, fighters and sea-launched cruise missiles have bombarded targets in Iraq and Kuwait since early Thursday, but many returning pilots are perplexed, even disconcerted, by the lack of more aggressive retaliation from Iraqi President Saddam Hussein's forces.

"If somebody was coming into my homeland, I would go after them a little bit harder than he came after us," said Col. John McBroom, commander of the 1st Tactical Fighter Wing, who flew in the second wave of attacks Thursday. "Up until this moment, I don't think he has become an adversary. I'm not sure why yet. We have not seen a great deal today. . . . It could mean that they want to wait us out.

"Just remember, this is only the first day of a war, not necessarily the conclusion of it. And even though he didn't come up much today, we know he has some aircraft, he has some pilots. We are still waiting for him to do that."

That Iraq was able to fire missiles into Israel today after 24 hours of massive allied bombing indicated that, despite the extraordinarily optimistic reports issued in the early hours of the air war against Iraq, allied pilots did not hit everything they had targeted.

Military authorities noted today, even before the Iraqi missile attacks, that hundreds of targets remain untouched and that planes will have to make second attempts to hit dozens of sites that bombs or missiles missed or failed to destroy during Thursday's first strikes.

U.S. missiles and American, British, Saudi, Kuwaiti and French aircraft hit a wide swath of targets across Iraq and Kuwait. Carrier-based bombers and attack planes struck missile and other targets near Iraq's borders with Israel and Turkey, and conducted bombing raids on dozens of airfields and Iraqi defense headquarters in Baghdad.

By early this morning, more than 120 low-flying U.S. Tomahawk cruise missiles were scheduled to have been launched from the sea surrounding the Arabian Peninsula. Navy officials said satellite reconnaissance photographs and other intelligence indicate that in the initial wave of 50 to 52 missile launchings, only one missile missed its target. Officials said they have not assessed the result of the remaining launches.

The U.S. fighters and bombers are dumping a broad range of deadly new weapons on targets in Iraq and Kuwait, including cluster bombs designed to destroy airfield runways and fuel air explosives that spew fine mists of fuel when ruptured, setting the air on fire and sucking the oxygen from the lungs of all nearby troops.

U.S. military officials, concerned that the huge concentration of air forces could result in allied planes mistakenly shooting each other, carefully orchestrated the attacks by spacing out both flight times and targets. Simultaneous with much of the air action, Tomahawk missiles were launched from the battleship USS Wisconsin and other Navy vessels at heavily defended targets throughout Iraq.

While many pilots reported that they evaded a rain of antiaircraft gunfire and surface-to-air missile launches, they encountered little resistance from Iraqi forces during the earliest nighttime attacks.

With more than 1,500 missions flown by early this morning, allied forces reported the loss of only four aircraft -- two from Britain, and one each from the United States and Kuwait. A U.S. Navy pilot was killed when an Iraqi surface-to-air missile destroyed his F/A-18 Hornet over Iraq. The Pentagon identified him as Navy Lt. Cmdr. Michael S. Speicher, 33.

At the same time, only one American pilot has thus far reported shooting down an Iraqi aircraft.

Capt. Gentner Drummond of Osage County, Okla., said some Iraqi planes fled north -- apparently to air bases there -- in "a preservation move."

"If they had sat on the ground, they'd have been bombed," Drummond said. "Had they flown in our direction, they would have been shot down."

Even without a major defensive effort by the Iraqi air force, British Tornado attack pilot Flight Lt. Ian Long portrayed the predawn assault as "the scariest thing I've ever done."

"It was absolutely terrifying," said the British Royal Air Force pilot. "You're frightened of failure, you're frightened of dying. You're flying as low as you dare, but high enough to get the weapons off."

Long said he drove his bomb-laden attack jet "very fast and very low" toward its airfield target, watching the skies to the right of his cockpit erupt into blasts of antiaircraft fire.

"We were trying to avoid bits of flak," said Long. "We saw some tracers coming off the target down our left side. We tried to avoid that. As the bombs come off, you just run -- run like hell."

Air Force Col. George Walton led one of the first squadrons of F-4G Wild Weasel electronic warfare jets into the skies over the Iraqi capital. "There was a lot of ground fire. We were shooting the surface-to-air missiles around the perimeter of Baghdad. We fired at two SAMs, but I don't know if we hit them both."

Walton said he emptied his pockets of all personal possessions before climbing the ladder to his cockpit, so that if he were captured by Iraqi forces they would learn no more about him than the rudimentary information engraved on his dogtags. "I've been saying prayers since we got here," Walton said.

Pilots who made daylight runs later today reported more intense antiaircraft fire. "The kitchen sink was coming up through the clouds," one said.

Col. Dave Eberly complained of another problem encountered Thursday afternoon by some pilots -- bad weather. A raid by about three dozen F-16A fighters encountered heavy cloud cover and many pilots, unable to see their targets, returned to base with their full bomb loads, Eberly said.

Meanwhile, as the intensive air raids dominate the first days and possibly weeks of the war, ground troops are beginning to move into attack positions closer to the Kuwaiti border.

A three-brigade army engineering group began packing Thursday for deployment closer to the front lines. When the ground war begins, part of the unit's mission could include reaching the heavily fortified Iraqi tanks and infantry entrenchments, clearing minefields and barbed-wire obstacles.

"We have been studying a long list of all the mines the Iraqis have," including some with special switches and sensitive triggering devices that "are difficult to disarm and disable," said Spec. 4 Charles Vondal, a 20-year-old North Dakota native and a combat specialist for the engineering unit.

Near the engineering encampment, a Saudi highway was jammed with westbound trucks, tanks, armored personnel carriers and other military vehicles also moving to new locations in the desert.

In another area of the desert, U.S. military forces reported that Iraqi artillery units shelled the Saudi border post of Khafji on Thursday, driving some citizens and Saudi soldiers from the area and touching off a major fire in a nearby oil refinery.

As a massive column of black smoke rose into the air, U.S. military officials attempted to screen the fleeing citizens for possible Iraqi-controlled terrorists.

A Kuwaiti official living in exile in Saudi Arabia said Thursday that doctors at two Kuwaiti hospitals told him they have been overwhelmed with hundreds of wounded Iraqi soldiers as a result of U.S. and allied attacks inside Kuwait. U.S. military officials said they could not confirm those reports.