The presidential jumbo jet, known as Air Force One, is loaded with advanced military technology, including sophisticated anti-missile defense systems.

But the main security measure employed for President Bush's trip to Iraq was secrecy. The White House let it be known that Mr. Bush would be spending Thanksgiving with family members at the president's ranch in Crawford, Texas, even going so far as to release the dinner menu to the news media. There was no mention of any trip.

The president slipped away from the ranch in an unmarked vehicle for the drive to a nearby airport, where he climbed aboard Air Force One using the rear stairs rather than the front.

The number of people with advance knowledge of the surprise voyage was kept to an absolute minimum. Air Force One flew into Baghdad under the cover of night with its lights darkened and windows closed.

"The major consideration, of course, is operational security," said Retired U.S. Army Colonel Ken Allard, now a military affairs analyst, spoke on the MSNBC television network. "The fewer people that know, the better the opportunities [chances] of keeping it secret. One would imagine that the flight [into Baghdad] observed absolute radio silence with no overt signs that it was Air Force One - all the things you could think of to give George Bush a low profile were observed."

News of the president's trip was kept secret until after he left Baghdad.