Airlines and airports in the UK were preparing for another difficult day today in the wake of yesterday's airport security alerts and new security measures.A ban on virtually all carry-on luggage remained in place, and passengers were told to expect extended delays at checkpoints.

OAG calculated that an estimated 400,000 passengers were impacted in the UK as more than 3,800 flights were scheduled to take off on Thursday, of which 3% were transatlantic. More than 650 flights were planned to depart from London Heathrow. Of these 11%, representing 76 flights and 22,384 seats, were destined for a US airport.

British Airways cancelled approximately 400 mainline services, about half of its normal flying program, predominately domestic and short-haul services to and from Heathrow and London Gatwick on Thursday. It said it anticipated operating around 60% of its scheduled 400 short-haul and domestic services and around 75% of its scheduled 150 long-haul services to and from LHR on Friday, including all long-haul services to and from every country with the exception of the US. Flights to and from the US are likely to continue to suffer knock-on delays as a result of enhanced security measures and may be subject to possible cancellations.

Bmi, the second-largest carrier at Heathrow, said it operated more than 66% of its normal LHR schedule. Out of 170 daily services it cancelled 58 flights. It said it anticipated that all airlines within the bmi group would be operating a full program of flights today. Most European carriers operating short-haul flights into Heathrow started canceling flights from midday and warned of further possible cancellations today.

EasyJet opted to cancel all flights from Gatwick, Luton and Stansted for a good part of the day as a result of the severe congestion caused by increased security checks at all UK airports. It intends to fly its full schedule today with the exception of services from London airports to a limited number of destinations, including Edinburgh, Glasgow, Aberdeen, Newcastle, Inverness, Paris, Geneva and Amsterdam. In order to keep airport disruption to a minimum, the LCC is opening its check-in desks 3 hr. before scheduled departure time.

Ryanair flights suffered delays at Stansted and the carrier said flights from other UK airports and flights between non-UK airports experienced knock-on effects.