Police said the aim of the plot was to detonate bombs smuggled on board aircraft in hand luggage.

"A major terrorist plot to allegedly blow up aircraft in mid-flight has been disrupted in a joint, pre-planned, intelligence-led operation by the metropolitan police anti-terrorist branch and security services," a police spokesman said.

He said police believes that the intention was particularly to target flights from Britain to the United States.

Police had arrested an unspecified number of people in London during the night. He gave no further details.