Today, Ryanair has threatened to sue the government over the security measures that have recently been imposed at airports. Since a plot to detonate bombs on planes traveling from the UK to the US was uncovered a few weeks ago, air passengers have faced tight restrictions on what hand-luggage they are allowed to carry, and stricter checks than were previously in place when boarding.

The measures have made air travel from the UK extremely difficult. Passengers have endured long delays, and many flights have had to be cancelled, negatively affecting airlines. A Ryanair spokesperson argued that the measures are unnecessary, and said that unless they were lifted Ryanair would be seeking compensation from the government for imposing them.

To support this claim that the security measures are unnecessary, the spokesman made a comparison with the 7/7 Tube bombings. After the bombings, he pointed out, the government got the Tube service back to normal within a matter of days. There is therefore no reason, he inferred, for the current security measures at airports to continue weeks after the plot to bomb aircraft was uncovered; things should be back to normal by now.

This argument overlooks important differences between the two cases; it draws a weak analogy. For example, the Tube bombings did not involve the discovery of any new threat, and so once the damage done had been repaired and the crime scene examined, things could return to normal. The discovery of the recent terrorist plot, however, raised a new danger: the possible use of liquid explosives. It therefore required new security measures to be introduced indefinitely.

This difference between the cases that the Ryanair spokesman compared means that the comparison can’t support the conclusion that he drew from it.