An aircraft cabin ban on large electronic devices was prompted by intelligence suggesting a terror threat to US-bound flights, say US media.
The US and UK have announced new carry-on restrictions banning laptops on certain passenger flights.
The so-called Islamic State group (IS) has been working on ways to smuggle explosives on to planes by hiding them in electronics, US sources tell ABC.
The tip-off was judged by the US to be “substantiated” and “credible”.
Inbound flights on nine airlines operating out of 10 airports in eight countries are subject to the US Department of Homeland Security ban.
Phones and medical devices are not affected.
US Secretary of State Rex Tillerson is hosting a two-day meeting of ministers and senior officials from 68 nations to discuss the threat from IS.
The Washington talks will be the first full meeting of the coalition since December 2014.
What is the meeting about? By Barbara Plett-Usher, US State Department correspondent
This will be a chance for the Trump administration to put its stamp on the global battle against the Islamic State group, and for the reticent secretary of state to put his stamp on a foreign policy issue that the president has identified as a priority.
The State Department says the meeting aims to accelerate efforts to defeat IS in its remaining strongholds: the Iraqi city of Mosul and the Syrian city of Raqqa.
On the campaign trail Mr Trump claimed to have a secret plan to obliterate the group. But his Pentagon has largely stuck with Barack Obama’s strategy of supporting local ground forces, albeit with increased US military participation as the assault on Raqqa nears.
Coalition members will also discuss how to stabilise and govern the cities after the conflict; and they’re looking to see if Washington remains committed to a longer term effort to secure the region.
What do we know of the threat?
Eric Swalwell, a Democratic member of the House Intelligence Committee, told ABC News there was “a new aviation threat”.
“We know that our adversaries, terrorist groups in the United States and outside the United States, seek to bring down a US-bound airliner. That’s one of their highest value targets. And we’re doing everything we can right now to prevent that from happening.”
Another member of that committee, Republican Peter King, told the New York Times he was forewarned about the ban.
“It was based on intelligence reports that are fairly recent. Intelligence of something possibly planned.”
The restriction is based, we are told, on “evaluated intelligence”, BBC security correspondent Frank Gardner writes.
That means that US intelligence has either intercepted discussion of a possible extremist plot or has been passed word of one by a human informant.
Which airlines are affected?
The nine airlines covered by the US ban are Royal Jordanian, EgyptAir, Turkish Airlines, Saudi Arabian Airlines, Kuwait Airways, Royal Air Maroc, Qatar Airways, Emirates and Etihad Airways.
The British ban, announced hours after the American measure, is similar but applies to different airlines, including British Airways and Easyjet.
It covers direct passenger flights to the UK from Turkey, Lebanon, Jordan, Egypt, Tunisia and Saudi Arabia.
On Wednesday, Easyjet passengers from Turkey and Egypt bound for the UK were already told to put large electronic devices in the hold.
The airline said passengers would face extra security checks and advised them to arrive early at the airport.
The 10 airports affected by the US ban are:
- Mohammed V International, Casablanca, Morocco
- Ataturk Airport, Istanbul, Turkey
- Cairo International Airport, Egypt
- Queen Alia International, Amman, Jordan
- King Abdulaziz International, Jeddah, Saudi Arabia
- King Khalid International, Riyadh, Saudi Arabia
- Kuwait International Airport
- Hamad International, Doha, Qatar
- Abu Dhabi International, United Arab Emirates
- Dubai International, United Arab Emirates
The airlines included in the US decision have been given a deadline of 07:00 GMT on Saturday to impose the ban, officials said, adding that the restriction had no end date.
However, an Emirates spokeswoman told Reuters news agency the airline understood that the US directive would come into effect on 25 March and remain valid until 14 October 2017.
What do you want to know about the electronics flight ban? Send us your questions and a BBC journalist will investigate and answer the most popular.
Use this form to ask your question:
If you are reading this page on the BBC News app, you will need to visit the mobile version of the BBC website to submit your question on this topic.