Delays are possible at UK airports throughout the summer following the bomb attack in Glasgow last Saturday and a stream of alerts this week.
Airport security will not return to pre-alert levels for the foreseeable future, despite the lobbying efforts of the industry.
The Department for Transport would not comment on existing or future measures, but sources insist restrictions on liquids, which apply across the European Union, will not be removed.
Random tests on the liquids will continue and be expanded in the autumn.
Hand searches at security will also continue, with the proportion of passengers subject to searches dependent on the level of alert. This rose to the highest level of ‘critical’ last weekend – meaning searches of everyone.
A significant proportion of passengers will also continue to be required to remove their shoes, in line with Government requirements.
The one restriction that may be modified is the UK limit on cabin baggage – but this will not change until after the peak holiday season at the earliest.
The single-bag limit causes particular problems among transfer passengers at Heathrow, who frequently arrive with the two bags allowed elsewhere.
Airlines hope limited tests will begin shortly at Heathrow on high-tech scanning equipment that would allow passengers to carry two cabin bags.
The tests will be undertaken at one of the airport’s flight connection centres and, if successful, the scanners could be deployed across Heathrow and other major airports in the autumn.
An airline source said: “They provide a technical solution and we want them in use as quickly as possible.”
However, the scanners might be restricted to transfer and fast-track passengers initially. They are expensive and may prove beyond the budget of many regional airports.