Increased U.S. fears of terror attacks may not be unfounded. The Hajj, the huge annual Muslim pilgrimage to Islam's holy city of Mecca, can provide cover for militant organizations attempting to secretly place operatives around the globe to stage attacks.

Four years ago, Usama bin Laden's relatives, worried about his ill health, tried to use the pilgrimage as a cover to visit the Saudi-born terrorist while he was holed up in Afghanistan, says a former Afghan airline official who was approached by the fugitive terrorist's family.

The sheer number of travelers for the five-day pilgrimage, which typically draws about 2 million Muslim visitors, means that tracking movements becomes difficult if not impossible ---- and would-be terrorists know it.

The U.S. government -- citing increased intelligence suggesting Al Qaeda activity -- upgraded its terror status to code "orange," on Friday warning of an increased possibility that the terrorist network would launch an attack to coincide with Muslim holy days.

During the 1999 Hajj, bin Laden's mother and brother apparently contacted officials at Afghanistan's state-run airline, Ariana, to sneak aboard a flight to visit the ailing terrorist in his Afghan hideaway.

A former airline official, speaking to The Associated Press on condition of anonymity, provided details of the attempt to smuggle the relatives into Afghanistan after he met a brother of bin Laden who identified himself only as Abdullah.

At the time, bin Laden was ill and United Nations sanctions had grounded Afghanistan's national airlines -- except for flights to Saudi Arabia for the pilgrimage.

"He was a tall, young, handsome man and he said 'we want to go because my brother is sick and my mother is insisting she goes to see him.' They said they had permission from the Saudis and from the foreign ministry in Afghanistan," the official recalled of the meeting held at the airport in Jeddah.

The former employee ---- the only non-Taliban among the Afghan men at the 1999 meeting ---- still lives and works in the Afghan capital, Kabul, and said he feared repercussions if identified.

The Taliban's vice president of commercial affairs at the airline, Mullah Kifaiatullah, and the Taliban's consular officer in Jeddah were the only two others at the meeting with the man, who was introduced by "a man who said he was with the Saudi interior ministry."

The meeting was held at the airport in Jeddah, after three calls within one hour to the Ariana employee's mobile phone by the Saudi interior ministry official.

"When we returned to the hotel after the meeting, the Taliban told me 'you don't tell anyone about this.' I was so scared about having this information. I didn't know what would happen to me and I wanted to just run away from Ariana after that, but I didn't know what would happen if I left Ariana."

In the end, bin Laden's brother and mother were not taken aboard the Ariana flight because United Nations workers were monitoring everyone who got off the aircraft back in Kabul, he said.

"I know for certain they did not come on the flight. I told his brother to try to go by way of Quetta or Peshawar," both in Pakistan because the U.N. would not be monitoring those flights.

"His brother smiled and said 'I've been to Quetta. It is so hot and to Kandahar (in southern Afghanistan) it is a long and dusty ride."' But Abdullah told the Ariana official he was in touch with his brother who could arrange transportation from the Pakistan border.

Today, even Pakistani investigators admit they are working to improve immigration controls throughout the year. Federal investigators in Pakistan said forged documents are a dilemma for law enforcement.

"It is very easy for any person to get a fake Pakistani passport with the help of those agents dealing in the business of forged travel documents," said Sharif Virik, a director at Pakistan's domestic agency, the Federal Investigation Agency.

"This is a serious problem, and we are very worried about it," he said. In 2001, Pakistani authorities stopped nearly 1,000 people trying to board aircraft using false documents.

"You can get ten passports of different countries, if you know who to approach," said Virik.

But the authorities are clamping down.

"We also seized forgery tools, and fake stamps of foreign missions," said Naeem Khan, regional chief of the Federal Investigation Agency.

But the traffic during the Hajj greatly increases the workload -- and the dangers of undesirables getting through. A total of 135,000 Pakistanis traveled to Saudi Arabia for the pilgrimage this year.

This year Pakistan imposed stricter controls on its pilgrims, said Brigadier Javed Iqbal Cheema, director general of the National Crisis Management Center.

In Afghanistan similar controls have been imposed on its 25,822 pilgrims who were given visas to Saudi Arabia. Their identities have to be verified by the head of their local mosque, then they are registered with the local police. However, returning pilgrims either in Pakistan or Afghanistan rarely get more than a glance.