A terror attack at Scotland’s Glasgow airport Saturday following two unsuccessful car bombings in London on Friday that could have killed hundreds have led the UK government to raise its security alert to the highest possible level in anticipation of more attacks to come.

Five bystanders were injured when two men drove a Jeep at high speed through the main terminal entrance of Glasgow International Airport two days ago. A “suspect device” was later found on one of the drivers and British security officials suspect the attack was a suicide mission. If security posts hadn’t put a stop to the vehicle, hundreds inside the airport terminal could have been killed, say witnesses.

A day earlier, police foiled a terrorist plot in London when they found two cars in central London packed with a deadly mix of gasoline, propane and nails. One car was found abandoned outside a night club and the other had been towed after it was found illegally parked close by. The cars had been abandoned in the heart of London’s entertainment district on its busiest night of the week, leading police to believe the plot was intended to kill perhaps hundreds of people.

Police believe the two incidents were linked; a security official said the methods used for both attacks were similar, with all three cars being packed with large quantities of combustible materials. Terrorism experts said evidence pointed to the attempted London bombings being orchestrated by a terrorist cell associated with al Qaeda.

Britain’s security alert is now “critical,” which is defined as “an attack is expected imminently.”

“We are currently facing the most serious and sustained threat to our security from international terrorism,” Britain’s new home secretary, Jacqui Smith, said.

The London and Glasgow attacks come one week before the second anniversary of the July 7, 2005, London transit bombings in which 52 people were killed.

Read “One Sip of a Bitter Cup” and the other articles in our special report that put the 7/7 London attacks—and the current threat—in their prophetic context.