AIRLINE passengers were plunged into chaos today after security forces foiled a terrorist plot to blow up a “number of aircraft” in mid-air.After nearly 20 people were arrested in the London and Home Counties, home secretary John Reid said: "The police believe the alleged plot was a very significant one indeed.

AIRLINE passengers were plunged into chaos today after security forces foiled a terrorist plot to blow up a “number of aircraft” in mid-air.

After nearly 20 people were arrested in the London and Home Counties, home secretary John Reid said: "The police believe the alleged plot was a very significant one indeed. At 2am this morning the Joint Terrorism Analysis Centre raised the UK threat state to its highest level - critical."

The swoops led a heightened level of security at all airports, culminating in:

N EasyJet cancelling flights out of Stansted Airport

N Some foreign airlines suspending flights to Heathrow.

N British Airways cancelling scores of flights including those to Munich, Barcelona, Madrid and Dusseldorf.

N Queues of traffic building up around all major airports.

N Hand luggage being banished to aircraft holds with restrictions on what could be taken on board flights.

N Passengers being told they could take a few items such as passports, medicines and nappies on board in clear plastic bags.

N All passengers' footwear, and the items they were carrying, being X-ray screened.

Stansted Airport websiteEasyjetRyanair