Early on Tuesday, the federal government notified airlines serving 10 airports in majority-Muslim countries that sometime before Friday, airlines will have to prevent passengers from carrying on laptops, tablets, or electronic cameras on flights from those airports to the US.

The “laptop ban” had been rumored throughout the day Monday, due in part to a since-deleted tweet from the Royal Jordanian airline. Initial reports made the new requirement seem sudden and hectic — and maybe, given the track record of the Trump administration with Muslim-majority countries, ideologically motivated.

But the official policy rollout was quickly endorsed by a key Democrat on a congressional intelligence committee. The United Kingdom followed up by announcing it would impose its own form of a laptop ban on certain flights, following the US’s lead.

There may very well be an intelligence case for the laptop ban — a specific threat that justifies requiring people to store their laptops in checked baggage rather than having them during flights. But it’s impossible to say for sure. Here’s what we know.

The “laptop ban” targets direct flights from 10 airports in Muslim-majority countries

Under the new policy, passengers on flights arriving in the US from 10 specific airports won’t be able to carry on any electronic device larger than a smartphone. Larger electronics — such as laptops, tablets/e-readers, and electronic cameras — will be allowed in checked luggage, but not as carry-ons.

The affected airports are all in majority-Muslim countries (many in the Middle East). However, the reach is broader than the countries affected by the Trump administration’s attempted ban on travel from several majority-Muslim countries; affluent Middle Eastern countries like Saudi Arabia and the UAE, left out of the travel ban, do have airports affected by the laptop ban.

Here’s the list of airports whose US-bound flights will be affected:

Egypt: Cairo International Airport (CAI) in Cairo

Cairo International Airport (CAI) in Cairo Jordan: Queen Alia International Airport (AMM) in Amman

Queen Alia International Airport (AMM) in Amman Kuwait: Kuwait International Airport (KWI) in Kuwait City

Kuwait International Airport (KWI) in Kuwait City Morocco: Mohammed V Airport (CMN) in Casablanca

Mohammed V Airport (CMN) in Casablanca Qatar: Hamad International Airport (DOH) in Doha

Hamad International Airport (DOH) in Doha Saudi Arabia: King Abdulaziz International Airport (JED) in Jeddah; King Khalid International Airport (RUH) in Riyadh

King Abdulaziz International Airport (JED) in Jeddah; King Khalid International Airport (RUH) in Riyadh Turkey: Ataturk International Airport (IST) in Istanbul

Ataturk International Airport (IST) in Istanbul United Arab Emirates: Abu Dhabi International Airport (AUH) in Abu Dhabi; Dubai International Airport (DXB) in Dubai

In a companion policy, announced Tuesday, the British government plans to put similar restrictions on flights entering the UK from all airports in Egypt, Jordan, Lebanon, Saudi Arabia, Tunisia, and Turkey — a slightly different list than the one used by the US.

The laptop ban is going to get rolled out, airline by airline, over the next few days

The deadline for airlines to implement the ban is early Friday morning Eastern time.

Airlines were notified early Tuesday morning, and “each airline has 96 hours during which they need to implement the changes,” according to Department of Homeland Security spokesperson David Lapan.

Some airlines, if they’re ready, might implement the electronics ban earlier than the deadline: “Some may take two days, some may take three days,” Lapan said. Passengers will have to comply with the ban whenever the airline puts it into effect. But the rollout of the ban wasn’t quite as sudden or hectic as initial reporting implied.

DHS implies that the laptop ban won’t last forever — but it doesn’t provide a specific end date, either. It’s going to evolve “as threats evolve.”

The ban might be based on specific intelligence of an upcoming plot — but the government isn’t saying that

It’s not common for the US to overhaul airport security requirements, and it’s even less common to do so at particular airports. But it’s not unprecedented, either.

In July 2014, for example, the US stepped up security for US-bound flights at several airports — including requiring passengers to turn on any electronic devices in the presence of airline employees before boarding the plane, to prove they were real electronics and not electronics-shaped bombs. The US government didn’t explicitly name the affected airports in public, but an official told CNN at the time that “the changes would primarily focus on airports in Europe and the Middle East.” (Those standards continue to be in effect at several airports, according to DHS.)

Usually, big changes to airport security are reactive — in response to specific plots, either thwarted in advance (like a 2006 plot to use liquid explosives) or unsuccessful (as with attempted “shoe bomber” Richard Reid in 2001). Those cases prompted the ban on bringing in outside liquids in containers larger than 3 ounces, and the requirement to put shoes through TSA screeners, respectively.

In this case, it’s not clear there is a specific plot that DHS is trying to thwart or has thwarted. The fact sheet and FAQ on the DHS website says there’s new intelligence that warrants a new policy — but the specifics it offers are past plots on foreign planes:

We note that disseminated propaganda from various terrorist groups is encouraging attacks on aviation, to include tactics to circumvent aviation security. Terrorist propaganda has highlighted the attacks against aircraft in Egypt with a soda can packed with explosives in October 2015, and in Somalia using an explosives-laden laptop in February 2016.

That said, some security experts say the rollout of the policy is consistent with what the government would do in the face of a specific threat. “It just feels like there was an intel briefing that they had,” former TSA head Kip Hawley told Wired.

The fact that the UK is following the US’s lead in banning some devices on some flights buttresses the idea that there’s a specific threat in play. So does the fact that at least one prominent Democrat — California Rep. Adam Schiff, the ranking member on the House Intelligence Committee — is backing up the Trump administration’s decision:

To those worried that Trump admin won't be trusted in a crisis, note that Dems can prevent this by backing admin actions. Low-level example: pic.twitter.com/aKpEINKXNj — Eric Geller (@ericgeller) March 21, 2017

The irony of stepping up security is that it’s easier to justify a new policy by pointing to something that’s already happened — like the “shoe bomber,” for example. But by that point, you’re trying to prevent the last attack. Being proactive sometimes means banning laptops first and answering questions later.

It’s a very easy power for the government to abuse — especially one with the track record the Trump administration has of stirring up fear on issues like crime and unauthorized immigration, when the reality doesn’t justify being afraid. But the fact that other governments and key Democrats are stepping in to validate the administration’s decision is evidence that this time might be legitimate.

It’s harder to blow up a plane from the luggage hold — but it’s easier to start a fire

The key question about the laptop ban is whether it would actually prevent a terrorist attack. After all, it’s just as possible to blow up a device in the baggage hold as it is in the passenger cabin.

Lapan, the DHS spokesperson, declined to explain why the government thinks the passenger cabin is a bigger risk; “we’re not able to talk about the specific details of security requirements,” he told Vox. But Hawley told Wired that a bomb could do less damage in a cargo hold. A small bomb is likely to damage only other luggage, instead of people; a bigger one would have to contend with the fact that the cargo hold is heavily reinforced. “You really need a big bomb to knock a plane down underneath the floor,” he said.

The bigger risk with putting laptops in the baggage hold is battery fires. Some electronic devices have lithium-ion batteries that could catch fire in the air — and it’s a lot easier to spot and put out a fire in a cabin full of people than in a baggage hold. Lapan said that DHS has given advice to the airlines affected by the ban about how to “minimize safety risks associated with placing additional lithium battery–powered devices in checked baggage.”

Ideally, airport security employees catch any bombs before they get on the plane to begin with. At one of the airports affected by the ban — Abu Dhabi International Airport — US Customs and Border Protection officials “preclear” all luggage (as well as passengers) before boarding, allowing them to skip full screening once they arrive in the US. In other airports, it’s the responsibility of airport officers to screen baggage. But the hope is that they’ll be able to spot bombs hidden in laptops the same as they could spot any other bomb.

Is this a “Muslim laptop ban”?

It’s impossible not to notice that all the affected airports are in majority-Muslim countries — especially given that the Trump administration has a history of targeting majority-Muslim countries in the name of national security. (See: travel ban 1.0; travel ban 2.0.)

The targeting has inspired a lot of skepticism about how legitimate the threat really is. “This could be the latest in what looks set to be a long line of discriminatory measures deployed by the Trump administration against Muslims around the world,” said Naureen Shah of Amnesty International USA in a statement. “This administration has consistently used ‘national security’ as shorthand for discriminating against Muslims, and we fear this latest decision may be no different. Muslims are once again left in the dark as the U.S administration piles up bans and restrictions against them.”

It’s worth noting, for what it’s worth, that the ban doesn’t exempt particular passengers — even though it has the opportunity to do so. US citizens, people with preclearance through the TSA’s Global Entry program, and even US diplomats are subject to the laptop ban. On its own, this doesn’t prove that the ban doesn’t have malicious intent (just like the fact that the travel ban didn’t ban only Muslims wasn’t enough to persuade judges it wasn’t discriminatory), but it’s a good point to bear in mind. Security expert Brian Jenkins told Bloomberg News that the government might be concerned about conspiracies involving airport or airline employees, rather than passengers themselves.

Others (including George Washington University professor Henry Farrell) have speculated that the policy is a product of economic protectionism. Over the past several years, airlines such as Turkish Airlines and Emirates have increasingly marketed themselves to US travelers as international hubs — encouraging travelers to fly through Istanbul or Dubai to their ultimate destination for a cheaper or more luxurious experience. American and European competitors believe these airlines are able to offer cheaper fares because they’re getting government subsidies.

President Trump has a known affinity for protectionism, and recently met with the heads of several US-based airlines. It’s possible to imagine that he’s now throwing them a bone, by forcing American travelers — especially those in business class and first class — to choose between a cheaper fare on a foreign airline and the ability to get work done or keep children engaged on a long flight with a domestic one.

The fact that the UK appears to be following the US’s lead on banning laptops certainly makes this theory less likely — though some British Airlines flights will be affected by the UK’s ban (due to the different countries it covers), while no US airlines will be affected by the US version. The supportive statement from ranking House Intelligence Democrat Schiff also indicates that there’s more going on here than economic protectionism.

It’s possible the Department of Homeland Security is cooking up a nonexistent threat to justify a target on majority-Muslim countries or on foreign airlines. But it would have to have successfully hoodwinked both the intelligence services of US allies, and key Democrats — and both of those groups have good reason to be skeptical of the Trump administration right now. So it seems entirely plausible that the motive here is at least partly genuine. The question is how it will be used by the administration — and whether the ban will, in fact, go away if the potential threats recede.

CORRECTION: This article originally said that Customs and Border Protection “precleared” travelers to the US from Dubai International Airport; the airport in the UAE with preclearance is actually Abu Dhabi International Airport.