The world is indebted to British counter-terrorism officials for intercepting a plot to blow up several passenger planes over the Atlantic. If the plotters had succeeded, thousands of people could have perished. Even though the plan failed, air travel will not go unscathed.

The information released by British authorities makes clear that terrorists still see the aviation system as a target for their lethal conspiracies. In this case, the apparent plan was to have suicidal terrorists board planes as passengers and mix and detonate explosive liquids or gels once airborne.

Aviation security experts have long been aware of this hazard, but have not insisted on the step needed to prevent it: the prohibition in hand baggage of any liquids or gels. Now the US Transportation Security Administration has decided to enforce such a ban.

The focus on carry-on luggage should not obscure concern over another weak link in the system: the commercial cargo that even passenger planes carry in their holds.

The federal government should mandate 100 per cent inspection or prohibit cargo on passenger planes, whatever the impact on profits of the shippers or the airlines. Passengers, their hand baggage, and their checked luggage are all screened. Commercial cargo should be, too.