A ban on laptops and tablets in cabin baggage on flights from Turkey and some countries in the Middle East and North Africa to the US and UK has come into effect.
Officials say devices “larger than a smartphone” must travel in the hold because of an increased risk that they could contain explosives.
At least one airline is allowing devices to be used up until boarding.
The US ban covers eight countries, while the UK restrictions apply to six.
Nine airlines from eight countries – Turkey, Morocco, Jordan, Egypt, the United Arab Emirates, Qatar, Saudi Arabia and Kuwait – are affected by the US ban. They operate about 50 flights a day to the US.
UAE airline Emirates is offering complimentary packing and shipping services at gates to enable passengers to use their electronic devices after check-in and until boarding.
That also means passengers flying on two-leg trips from other countries to the US through Dubai can use their laptops on the first leg of their flights.
The UK ban meanwhile affects all flights out of Egypt, Turkey, Jordan, Saudi Arabia, Tunisia and Lebanon.
The British ban applies to any device, including smartphones, larger than 16cm (6.3in) long, 9.3cm (3.7in) wide or 1.5cm (0.6in) deep. However, most phones will be smaller than the limit.
Turkish President Recep Tayyip Erdogan has urged the US and UK to lift the bans as soon as possible.
Testy times we live in.