Transportation Security Administration personal checks traveler's identification at Chicago O'Hare International Airport on Friday, Nov. 1, 2013. A gunman armed opened fire at Los Angeles International Airport on Friday, killing a TSA employee. Flights were disrupted nationwide. (AP Photo/Nam Y. Huh)

Thousands of fliers across the U.S. were delayed Friday after a shooting at Los Angeles International Airport closed parts of the airport. A prolonged shutdown at the nation's third largest airport will be particularly troublesome for those hoping to head to the East Coast or across the Pacific Ocean.

Flights bound for Los Angeles that had not yet taken off were held at their gates by the Federal Aviation Administration. Others in the air — including three JetBlue flights from the East Coast — diverted to other airports.

Gina Marie Lindsey, executive director of Los Angeles World Airports, which operates LAX, said at a press conference that planes are landing at the airport at "less than half the normal arrival rate."

The shooting occurred around 9:30 a.m. local time. Some passengers who landed after the shooting spent at least two hours sitting on planes parked in a remote corner of the airport.

Travelers trying to fly out were unable to reach the airport because of large road closures.

Lindsey said it will take "quite a deal of time" to get operations back to normal at the airport. She said it will be a "carefully orchestrated logistical ballet."

Passengers were advised to wait at nearby hotels until they hear more information about flight resumptions.

Los Angles is a major gateway for flights to Asia, Australia and New Zealand. Domestically, the largest cities served are: San Francisco, Las Vegas, New York, San Jose, Calif., San Diego and Phoenix.

However, it is not a major connection point such as Chicago, Atlanta, Dallas and Minneapolis.

Flight tracking site FlightAware.com said that as of 11 a.m. Pacific there were 12 flight cancellations and 132 flight delays to or from Los Angeles. To put that in perspective, there were 246 other flight cancellations Friday nationwide, mostly in New York and Philadelphia because of rain and heavy winds.

United Airlines, which operates out of terminals on the other side of the airport from the shooting, has issued a waiver for people traveling through Los Angeles, allowing them to change flights without paying a fee. Other airlines are expected to issue similar waivers.

"This situation is continuing to develop, and at this time we do not know the full extent of the impact to our operations," United spokeswoman Jennifer Dohm said via email.

JetBlue diverted flights from Boston, New York and Fort Lauderdale, Fla. to nearby Long Beach airport. Southwest diverted at least one flight — a trip from Chicago that landed in Denver.

Allegiant Air, which operates out of the terminal where the shooting occurred, had most of its flight depart prior to the incident. One flight to Bellingham, Wash. is delayed.