The overnight operation was meant to underscore that the U.S.-led military attacks carried out simultaneously were not aimed at civilians.

The cargo planes were airborne for 24 hours, dropping the packets from high altitudes onto areas in southern and eastern Afghanistan where the civilian need was deemed greatest.

"It did present dangers with the high altitude and the potential ground threat," Air Force Col. Bob Allardice told reporters at the United States' Ramstein Air Base in southwestern Germany after the planes landed.

He would not comment on whether the planes encountered any hostilities, but the 20-person crew, attached to the 437th Airlift Wing at Charleston Air Force Base in South Carolina, was unharmed and in high spirits.

One of the flight commanders, whose name was withheld due to security concerns, described the mission covering 6,000 miles from Ramstein to Afghanistan and back again as difficult, but uneventful.

The airdrop over Afghanistan was executed at higher altitudes than ever before attempted to avoid any enemy fire, the commander said, without specifying the altitude. Food drops previously have been made over Iraq, Bosnia, Kosovo and Somalia.

"That's the way you want it to be over the drop zone, boring. And it was," the commander said. "There was a haze on the ground and a couple of lights but we couldn't see anything else."

The packets were dropped from the back of cargo planes. To do that, the cabin and cockpits were depressurized, requiring crew to put on oxygen masks and endure near-freezing temperatures. Medical crew were on board both planes to make sure the flight crews didn't experience altitude sickness, he said.

"It was an outstanding success. It's a testament to the professionalism and the dedication of the crews and people supporting them," the commander said. "An unprecedented mission. A difficult one."

The packets contained a day's ration of red beans, rice, fruit bars, peanut butter and strawberry jam, providing at least 2,200 calories. The food does not contain any animal products so as not to violate any religious or cultural practices. Muslims, for example, do not eat pork.

The yellow plastic packets are about the size and weight of a hardcover book, and are designed to flutter to the ground rather than drop straight down to minimize the possibility that they could hit and injure someone. They have a picture of a person eating from a pouch, a stencil of an American flag, and this greeting in English: "This food is a gift from the United States of America."

The military also dropped leaflets and made radio broadcasts into Afghanistan to explain the U.S. action and make clear the targets are directed at terrorists and not ordinary Afghan citizens.

"To say that these attacks are in any way against Afghanistan or the Afghan people is flat wrong," Defense Secretary Donald H. Rumsfeld said Sunday night in Washington.

The United States has a stockpile of about 2 million of the food packets. More drops are planned but officials refused to say when they would take place.