New technologies being developed in Europe would make it impossible for hijackers to fly airplanes into buildings, The Sunday Times reported on Sunday. Systems using biometrics, which scan irises and fingerprints, would prevent unauthorized users from gaining access to cockpits and from operating the airplane's controls. If the airplane was headed for a collision with a building or terrain, another on-board system would automatically cause it to divert. That technology is based on mid-air-collision alert systems already in use. Another system, which was tested last month, comprises hidden cameras and microphones that can monitor every passenger and their conversations. This may prove alarming to privacy advocates, the Times said, especially if lavatories are also monitored. Yet more technological fixes in the works include explosive-sniffing detectors that could be placed at the doors of every airliner and computer chips that match luggage to passengers on board. The systems are expensive and how they would be paid for, or if airlines could afford them, is uncertain.