BOSTON – Amid new anxiety about air travel and tough new regulations about what passengers can bring on planes, at least seven U.S. flights on Friday were involved in security incidents. In one case, a stick of dynamite was found to have been aboard a flight.

The rash of events, safety consultants and others said, reflected both heightened emotions and appropriately tightened security in the wake of an alleged plot to blow up transatlantic airliners that was thwarted earlier this month by British authorities.

“I think it’s a combination of both,” said Douglas Laird, a Reno, Nev.-based consultant to the airline industry and former longtime security director for Northwest Airlines. “I think there is a heightened awareness of what happened in London, and that causes some people to overreact.”

In what may have been Friday’s most serious incident, authorities said, a college student’s checked luggage on a Continental Airlines flight from Argentina was found to contain a stick of dynamite after it landed in Houston en route to Newark, N.J.

A bomb-sniffing dog at the international arrivals area at George Bush Intercontinental Airport detected an explosive substance in a suitcase belonging to a man who told Houston authorities that he works in mining and often handles explosives.

The flight continued to Newark without the man or his baggage, and was swept again for explosives upon landing as a precaution, officials said.

The passenger, Howard McFarland Fish, 21, was charged with carrying an explosive aboard an aircraft and was in custody of U.S. Immigration and Customs Enforcement. Federal authorities have determined that his actions were not acts of terrorism, ICE spokeswoman Luisa Deason said in a statement.

Three U.S. aircraft – one each from American Airlines, U.S. Airways and Continental Airlines – made emergency landings on Friday.

A Transportation Security Administration spokesperson said American Airlines Flight 55, bound for Chicago from Manchester, England, was diverted to Bangor, Maine, because of “a reported threat to the aircraft while it was en route.”

FBI spokeswoman Gail Marcinkiewicz in Boston said she was unable to specify the nature of the alleged threat, but confirmed that the FBI was participating in an investigation in Bangor.

Marcinkiewicz said the plane was diverted to Bangor because it is the northernmost U.S. major airport. She said the plane carrying 188 passengers landed at about 12:45 p.m. Friday.

A TSA spokesman said that “given the current threat level, the agency, in conjunction with other federal authorities, took prudent action to ensure the security of passengers and crew.” The spokesman said TSA canines searched the plane.

Also on Friday, a Charlotte, N.C.-bound U.S. Airways jet that had taken off from Phoenix made a forced landing in Oklahoma City after a federal air marshal reportedly subdued an unruly passenger.

Authorities declined to give details pending an investigation.

After the crew of Continental Airlines Flight 2258 discovered a missing panel in the lavatory, the plane bound for Bakersfield, Calif., from Corpus Christi, Texas, was diverted to El Paso, Texas, according to the TSA.

The plane carrying 50 passengers was held for about four hours before officials determined there was no danger.

“The passengers were interviewed and the aircraft was thoroughly inspected with all the tools at our disposal, including canine teams,” said Pat Abeln, director of aviation at El Paso International Airport. “At the end of the day, this was a precautionary event that turned out to be a nonevent.”

In three other incidents, a utility knife was found aboard a parked U.S. Airways plane in Connecticut; takeoff of a United flight in Chicago was delayed after an onboard bomb threat; and, in Ireland, an Aer Lingus plane from the U.S. was evacuated after it landed.

Authorities in Hartford, Conn., boarded U.S. Airways flight 554 from Philadelphia on Friday morning after a passenger found a utility knife on a vacant seat. No arrests were made, and no threats issued, state police said.

At Chicago’s O’Hare airport, a flight attendant aboard United Flight 686 overheard a minor say he had a bomb, and alerted the pilot, who taxied to a secure part of the airport. The minor’s mother and the minor were removed from the plane and it was searched, an FBI official said.

After bomb-sniffing dogs found no explosives, the flight, which was on a layover between Portland, Ore., and New York’s LaGuardia, was allowed to continue.

And in Ireland, an Aer Lingus plane from New York was evacuated at Shannon Airport after police received a call early Friday claiming that “some sort of device” was on board. Police found nothing suspicious, Aer Lingus officials said Friday, and the plane returned to service.