Several international carriers, including Swissair, resumed flights to the United States at the weekend. Travellers faced long queues and check-ins amid tighter security measures demanded by the US Federal Aviation Administration (FAA).
Airlines issued lists of banned articles, including knives, and intensified searches of passengers and luggage on Saturday to comply with new FAA measures. International carriers were obliged to implement the measures in order to secure permission to resume flights to the US.
In Geneva, security delays were exacerbated by a three-hour strike by 500 Swissair employees to protest at the cash-strapped carrier's plans to cut 1,250 jobs. The Swiss carrier resumed flights to the US on Saturday, but warned passengers to expect significantly longer check-in times because of increased security and more thorough luggage searches.
At Charles de Gaulle airport outside Paris, crowds were so large that Air France ticket staff stood on top of check-in counters to call out passengers' names from waiting lists.
Britain's Transport Secretary, Stephen Byers, said he was considering posting armed guards on British airliners and ordering airlines to secure cockpit doors to foil suicidal attackers - precautions already in place on the Israeli airline, El Al.
Travellers using British airports have been forbidden to carry on board toy or replica guns, household cutlery - including knives of any kind - letter openers, corkscrews with blades, catapults, razor blades, tradesmen's tools, darts, scissors, knitting needles and sports goods such as rackets, cricket bats, golf clubs and pool cues.
Hypodermic needles are also forbidden, and travellers who need them for medical reasons will be asked for proof.
Silver cutlery replaced with plastic
Japan Airlines and All Nippon Airways said they were now conducting background checks on some passengers and scanning travellers and luggage more carefully. Both airlines also replaced silver cutlery with plastic.
In Frankfurt, Lufthansa announced that it had 21 flights to the US scheduled for Saturday.
Before checking in, passengers were required to send all their luggage through a scanner and at least one piece from each traveller was searched by hand, said Lufthansa spokeswoman Amelie Lorenz.
The Geneva-based International Air Transport Association (IATA) has called a meeting - expected to take place within the next few days - of its security committee to discuss ways of preventing hijackings, according to spokesman, William Gaillard.
IATA, which represents 266 carriers, says airlines around the world are facing losses and extra costs of around $10 billion (SFr16.6 billion) because of cancellations, delays and tighter security measures.
Gaillard said the US aviation market, which was still operating well below capacity on Saturday, was worth about $1 billion a day.
The crisis has already begun to hit some of the US's airline companies. Continental Airlines, the fifth-largest US carrier, said it on Saturday that it would lay off 12,000 employees and cut a fifth of its long-term routes due to the drastic decline in travel demand.
Northwest Airlines, the world's fourth largest commercial carrier, said it would cut its systemwide flight schedule by 20 percent by October 1, and would also review its overall staffing needs.
Just days earlier, regional US carrier Midway Airlines, already struggling under the weight of bankruptcy, completely shut down, laying off 1,700 employees.
swissinfo with agencies