Bad news for online travel companies...The US government is to tighten restrictions on electronic ticketing following Tuesday's tragedy on the East Coast. Instead of merely showing a photo identification at a check-in desk, passengers will have to show a printed receipt as well. E-ticketing has grown in popularity with the increase of online ticket sales, and the new security measures are likely to push up costs for online travel sites. Many airlines such as Dallas-based Southwest Airlines, which sells 80 per cent of its tickets online, will also be hit. Travellers will also have to show proof of a valid ticket to get past security checks within airports, though the responsibility for determining what will count as proof is being left up to individual airlines. The moves comes as part of a widespread programme of increased security measures aimed at preventing a repeat of Tuesday's horror as America's air transport infrastructure gets up and running. Meanwhile the International Air Transport Association was calling for widespread improvements in airport security, including the deployment of sophisticated biometric devices such as iris scanners and palm-print readers. The US transportation secretary ordered a full resumption of air travel from 11:00 (BST) yesterday, but airlines have been slow to put planes in the air, with British Airways saying that it will not resume flights to North America until it receives full details of improved security measures from the FAA.