Federal authorities have implemented new regulations for electronic airline tickets as part of tighter security at US airports, effectively taking away much of the convenience of online travel. Commercial airlines will no longer allow passengers holding e-tickets to receive a boarding pass by only showing photo identification. Passengers will have to present a printed receipt of their e-ticket purchase, according to representatives from online travel company Travelocity and Southwest Airlines. Also under the new restrictions, passengers will be required to show proof of a valid ticket to get past security checkpoints. The Federal Aviation Administration, which issued the guidelines, is leaving it up to each airline to decide what constitutes that proof. The FAA is encouraging customers to check in at the ticket counter instead of the at the gate. Some airlines are allowing e-ticketed passengers to print out confirmations of their receipts to show as proof. The changes in procedure are part of increased security efforts announced this week by the FAA in light of Tuesday's terrorist attacks in New York and Washington. Curbside check-in of baggage has also been forbidden, and knives of any kind will not be allowed on planes. In addition, the department said, carry-on baggage will be subject to search. Ticketless travel has been catching on in the United States since the emergence of airline ticket sales over the Internet. The benefits of an e-ticket were that a traveller did not have to wait for his or her paper ticket in the mail or risk losing the ticket. In addition, an e-ticketed traveller could avoid long airport lines by checking in at the gate, as long as he or she had a valid photo ID. Dallas-based Southwest Airlines said the tougher regulations could affect the company. Some 80 percent of the tickets it sells are e-tickets, and many of its customers check in at the gate without ever receiving a paper ticket, said Bob Kneisley, Southwest's associate general counsel. Kneisley said, however, that it is not clear how the regulations will be implemented on the ground. The majority of airline tickets sold by Priceline.com are also e-tickets, company spokesman Brian Ek said. Like Southwest, Ek said, Priceline is advising e-ticket customers to bring a printout of their travel receipt with them to the airport. Although that will unlikely obviate the need for them to go to the ticket counter, it should make the process easier, he said. E-tickets are popular because of the convenience they offer, but the new rules would strip them of a lot of their appeal, Ek said. "The whole idea of an e-ticket was that you could go directly to the gate and just give them your driver's license," Ek said. "You can't do that now." Southwest will station supervisors at security checkpoints in each of the airports in which it operates to inspect travel receipts, company spokeswoman Brandy King said. "For the time being, we will take those additional steps to make sure customers will be safe when they fly," King said. That sentiment was one that most of the airlines expressed about security amid their rush to provide customers with information on when flights would resume. Southwest plans to resume service Friday, according to a statement on the company's Web site. Southwest did not resume flying Thursday because some of the airports it serves have not yet opened fully and because of concerns about complying with new security directives from the government and the company itself, Kneisley said. The company is handling refunds on a case-by-case basis, encouraging customers to call its customer service centre with questions, King said. United Airlines also said it would resume operations Friday. Most of the other airlines, including Delta Air Lines and Northwest Airlines, authorised a limited number of flights Thursday but expected to resume normal operations Friday. American Airlines said its operations were focused on moving aircraft diverted on Tuesday to their original destinations. The airline said it expects to return to a full flight schedule in "several days". Travelocity and Expedia, another online travel agency, set up search engines where passengers could check their flight status for most of the airlines the travel agencies get tickets from. Web travel agency Orbitz advised customers to check the Web sites of the individual airlines. Priceline is taking reservations for air travel that begins after Monday and has resumed accepting reservations for all hotel and rental cars, Ek said. He did not say how the new regulations would affect Priceline or its customers. Customers with airline tickets from Priceline are unable to get refunds directly from airlines, Ek said. But Priceline will refund tickets for travel within the next three days, according to each airline's current refund policy, he said. See the E-commerce News Section for the latest headlines. See the Internet News Section for full coverage. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the Telecoms forum. Let the editors know what you think in the Mailroom. And read other letters.