Passengers can expect tight security, long waits

Air travelers in Los Angeles were greeted with tight security Thursday morning. Curbside and off-airport check-ins have been eliminated in all airports as part of the heightened measures.

(CNN) -- As air travel slowly resumes in the United States, passengers are discovering an entirely different experience at airports across the country.

The Federal Aviation Administration grounded all U.S. flights Tuesday and directed all U.S. airports to meet new heightened security guidelines after the terrorist hijackings and plane crashes.

The changes mean slower operations for airports and longer lines for passengers, who now must all check in at ticket counters now that curbside check-in is no longer an option.

AIRPORT OPENINGS Click for the status of major U.S. airports AIRLINE SCHEDULES Get flight information for the following airlines: * AirTran * Alaska * America West * American * Continental * Delta * Frontier * Northwest * Southwest * TWA * United * US Airways MORE STORIES Passengers can expect tight security, long waits      CNN.COM SPECIAL REPORT  CNN NewsPass Video  Agencies reportedly got hijack tips in 1998  MORE STORIES Intelligence intercept led to Buffalo suspects Report cites warnings before 9/11  EXTRA INFORMATION Timeline: Who Knew What and When? Interactive: Terror Investigation Terror Warnings System Most wanted terrorists What looks suspicious? In-Depth: America Remembers In-Depth: Terror on Tape In-Depth: How prepared is your city?  RESOURCES On the Scene: Barbara Starr: Al Qaeda hunt expands? On the Scene: Peter Bergen: Getting al Qaeda to talk RESOURCES Click for the FAA's full list of airport openings

Among the new restrictions:

* A total ban on knives of any material. Previously, knives with blades shorter than 4 inches had been allowed.

* Curbside and off-airport check-ins has been eliminated.

* All but ticketed passengers will be prohibited from proceeding past airport metal detectors.

* The use of federal air marshals, common in the early 1970s during a spate of hijackings, will be stepped up.

* More officers will be on duty at the nation’s airports.

* There will be more physical checks on passengers.

* Airport security screeners will be required to meet higher standards, and the contractors who supply the security personnel will be required to report to the FAA.

The Justice Department is assisting with security staffing, CNN has learned. It has ordered as many as a thousand federal security officers to boost airport and jetliner security.

An undetermined number of federal marshals, along with about 400 U.S. Customs Agents and 300 Border Patrol agents, are being dispatched to large airports across the country, law enforcement officials tell CNN.

The Marshals Service says an undisclosed number of deputies are being drawn from around the country to help provide security at more than a dozen of the nation's busiest and most important airports.

CNN Correspondent Patty Davis reports a source close to the airline industry has called on the FAA to nationalize or federalize the security checkpoints. So far, the FAA would not comment on that. Currently, the cost of security checkpoints is subsidized by the airlines.

Aviation and regulatory sources have not been able to say whether the variety of new security measures will be permanent or temporary.