Airport officials from around the world are cautioning passengers to "pack lightly" and arrive early as delays continue following Thursday's arrest in Britain of key figures in an alleged plot to blow up U.S.-bound airliners.
British officials are asking passengers Friday to arrive prepared for security checks. Travelers should have no hand luggage and items like prescription medicine should be kept in clear plastic bags. Long lines are reported at Heathrow Airport, with many flights being canceled.
Asian airports have introduced new security measures Friday as well, banning all liquids and gels from cabins.
New Zealand also banned the substances from flights to Britain and the United States.
U.S. authorities have designated all U.S.-bound flights from Britain under a "severe" threat level, the highest level of alert. All other international flights are operating under a "high" threat level.