At least one man claiming to be a pilot has been arrested and up to nine others detained in at least two of New York's three area airports, as officials probed the possibility some of those held were carrying knives, tickets booked for flights Tuesday morning and might be hijackers.

The arrest and detainments caused the immediate closure of all three of the city's airports, which had opened just hours earlier. Peter Yerkes, a spokesman for the Port Authority, which runs the airports, said planes in the air were being allowed to land, but no planes were allowed to take off. The hold went into effect shortly before 5 p.m.

A source knowledgable of the workings of the airline industry said the man arrested at John F. Kennedy International Airport checked in sometime between noon and 4 p.m. The man was trying to board American Airlines flight 299 bound for San Jose.

The man had been scheduled for an earlier flight on Tuesday bound for Los Angeles, but that flight was canceled after the terrorist attack began on the World Trade Center, the source said. A subsequent strip search found the man had a pilot's certificate from a Florida school, the source said.

The FBI was already investigating whether an altercation at Kennedy Airport on Tuesday was linked to the World Trade Center explosion, a law enforcement source told The Associated Press on Thursday.

The Tuesday incident occurred about 9 a.m. -- the same time two hijacked jet airliners crashed into the World Trade Center towers, toppling the two 110-story buildings. The source said the FBI is investigating whether the incident may have been an aborted hijacking attempt.

After the plane was boarded, United Airlines officials told passengers that United Airlines Flight 23, bound for Los Angeles, had been cancelled. Three males traveling refused to disembark. The argument with a member of the flight crew became so heated that the crew member called airport security. But before security arrived, the men had vanished, said the source, who spoke on the condition of anonymity.

On Thursday, according to the airline industry source, a man presented a ticket for Tuesday's Los Angeles flight at the counter -- but told airline employees that he had changed his mind and now wanted to travel to San Jose.

People at the ticket counter were suspicious, but they changed the ticket and alerted a supervisor who, in turn, notified Port Authority police. Authorities tracked the man to the gate, where he passed through security checks, including metal detectors. He was then stopped at the gate by security.

A short time later, three more men arrived at Kennedy and boarded American Airlines flight 133 to Los Angeles. Minutes later, law enforcement officers secretly boarded the plane using a catering cart, according to the industry source. The officers, with weapons drawn, then removed the three from the plane.

The industry source was unable to account for the other two people detained.

ABC News reported Thursday night that 10 people in all were detained trying to board flights at JFK and LaGuardia. They included nine men and one woman carrying knives, false identification cards, and flying licenses/certificate from Flight Safety International in Vero Beach, Fla. Four men and a woman were detained sometime before 5 p.m. at JFK, ABC said. Another five were detained between 7:30 and 8:15 p.m. at LaGuardia.

Early Friday, U.S. and Philippine authorities raided a hotel in the Philippines in connection with the attacks, Philippines President Gloria Arroyo said.

Arroyo, speaking at a Tokyo news conference, said the "joint action" was taken at the Bayview Hotel, which is near the U.S. Embassy in Manila.

The investigation was fueled by the discovery of the black box from United Airlines Flight 93 in Pennsylvania and the reception of a signal from the black box of the plane that crashed at the Pentagon.

Search crews will not be able to retrieve the black box at the Pentagon, which could contain information about the last minutes of American Airlines Flight 77, until they are able to enter the collapsed area of the Pentagon, where the plane's fuselage rests.

They were to begin moving into the collapsed area sometime Thursday night, said Arlington County Fire Capt. Scott McKay.

The Justice Department said Thursday that at least 18 hijackers were on the four planes that crashed; two planes with five and two with four. There are reports Thursday that up to 50 suspects have been identified, with 40 accounted for, many of them dead, and 10 missing.

Meanwhile, one person was arrested Thursday in connection with the attacks in Hamburg, Germany, Fox News has confirmed.

"Most of it today points to Usama bin Laden but the speculation at the end of the road is that he and his network were very much involved with Hezbollah, Fatah" and other terrorist organizations, Sen. Charles Grassley said.

FBI Searches Florida

On Wednesday, a Venice, Fla., man said FBI agents told him that two men who stayed in his home in July 2000 while training at a local flight school were two of the hijackers. Charlie Voss said agents identified the men as Amanullah Atta Mohammed and Marwan Alshehhi.

FBI agents "informed me that there were two individuals that were students at Huffman Aviation, my employer, and FBI told me they were involved in yesterday's tragedy," Voss said.

A former employee at a Florida flight school where some of the terrorists may have trained said Atta and Marwan had arrived from Germany in July 2000, reports say.

Federal agents had warrants to search the Florida homes of at least four men listed on the manifest of American Airlines Flight 11, The Miami Herald reported Thursday.

Some of the FBI agents sought information on a graduate of Embry-Riddle Aeronautical University in Daytona Beach, The News-Journal of Daytona Beach reported.

Citing two unidentified law enforcement sources, the newspaper reported that Waleed Al Shehri, 25, was listed as a passenger on the American Airlines flight that left Boston and crashed into the World Trade Center.

FBI agents removed student files from the Florida Flight Training Center, which is down the street from Huffman Aviation and offers the same type of pilot training. School owner Arne Kruithof would not give specific information about what the agents were seeking but said one of the files was related to a student from Tunisia.

Agents in Vero Beach asked Hank Habora about a neighbor, Amer Kamfar, 41. Kamfar was licensed as a flight engineer to fly turbojets and listed a Saudi Airlines post office box as his address in FAA records.

Federal agents were also interviewing Adnan Bukhari, who worked for Saudi Airlines and was in Vero Beach for more flight training.

Landlord Lonny Mixel said Thursday the tenant in the house adjacent to Bukhari's was Abdulrahman Alomari, who he said arrived in July 2000 and told him he was a commercial pilot from Saudi Arabia and was in Vero Beach to attend Flight Safety Academy.

Alomari said he would be out of the house by the end of August 2001. Then he pushed the date back until Sept. 3 and moved out that day.

Alomari told Mixel that he knew Bukhari.

Bukhari and his wife began renting a home from Paul Stimelind in June 2000, Stimelind said.

The couple's lease was up Aug. 31, but Bukhari asked for a two-week extension, through Sept. 15.

Stimelind said Bukhari told him he would be leaving by Sept. 17.

"He never gave a reason," Stimelind said. "He said he had a couple of things to clear up."

Attorney General John Ashcroft said authorities believe the hijackers were professionally-trained pilots. At least one hijacker on each of the four planes was trained at a U.S. flight school, authorities say.

The London-based Ash-Sharq al-Awsat newspaper reported Thursday that the Taliban forced an Afghan pilot and a retired Pakistani general to train 14 young Arab, Afghan and Pakistani radicals how to fly in Afghanistan.

The group was said to have left Afghanistan a year ago and to carry European passports.

Eyes on bin Laden

Officials were said to be focusing their efforts almost exclusively on bin Laden, who had recently warned of massive attacks against the United States.

Secretary of State Colin Powell said Thursday that bin Laden was a "prime candidate" in the attacks. He denied, however, that bin Laden was a suspect.

Early evidence, including communications between bin Laden supporters discussing Tuesday's attacks, indicated the attacks were tied to the suspected terror mastermind.

Bin Laden congratulated the people who carried out the attacks but denied that he was involved, a Palestinian journalist said.

Authorities were also investigating a possible network of bin Laden supporters in Boston.

At least one set of hijackers thought to have ties to bin Laden is believed to have crossed from Canada en route to Boston, from where two of the deadly flights launched.

Officials confirmed a car containing an Arabic language flight manual was confiscated at Boston's Logan Airport.

Abu Dhabi Television in the United Arab Emirates reported that two men with Saudi Arabian passports and international drivers licenses issued in the UAE were linked to the Mitsubishi sedan.

Officials said authorities were gathering evidence about four terrorist cells that may have had prior involvement in earlier plots against the United States. Those include the USS Cole bombing in Yemen and the foiled attack on U.S. soil during the millennium celebrations.

Bin Laden is linked to both of these plots, as well as the 1998 U.S. embassy bombings in Africa.

Other Leads

Fox News has confirmed that 2 weeks ago, American Airlines issued a memo to their employees to be on alert for imposter pilots after burglars broke into flight crews' rooms in Rome, stealing uniforms and ID badges.

The New York Times reported Thursday that a group of five men had set up video cameras aimed at the Twin Towers prior to the attack on Tuesday, and were seen congratulating one another afterwards.

The Associated Press contributed to this report.