The news came as a surprise on Monday night and, since the Trump Administration has yet to formally announce how this will work, travelers are struggling to make sense of exactly what is going on.

But based on reports, here’s what we know so far:

Which flights are affected?

The new device ban will reportedly affect flights to the U.S. that take off from ten airports in eight North African and Middle Eastern countries. Once again, the U.S. government has yet to publish an official statement. But reliable media outlets—including Fortune‘s sister publication TIME, the New York Times and the Washington Post—all report those same facts.

The airports in question are reportedly located in Jordan, Egypt, Turkey, United Arab Emirates, Qatar, Saudi Arabia, Morocco, and Kuwait. According to a deleted tweet (see below) from airliner Royal Jordanian, the destinations affected include New York, Chicago, Detroit, and Montreal.

The New York Times, meanwhile, says the new device ban only applies to foreign carriers, not U.S. airlines. (Update: the BBC reports that the U.K. has announced a similar ban on flights from six countries).

What devices are covered by the new ban?

The ban is clearly aimed at laptops, but does not include cell phones. As for other devices, including “phablet” phones, they may fall into a grey area at the discretion of the airlines. Note, though, that the Royal Jordanian tweet describes “laptops, tablets, cameras, DVD players, and electronic games.. etc.”

Here is a screenshot of the tweet, captured by Foreign Policy:

The tweet says medical devices are excluded from the ban. Other reports say the ban does not apply to flight crew members. For now, it appears passengers can stow their laptops in their checked luggage.

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When does the ban go into effect and how long will it last?

TIME says it went into place at 3 a.m. ET on Tuesday, but airlines reportedly have 96 hours to comply—meaning it will be in force by late Friday night.

Officials initially described the ban as indefinite. But a spokesman for the Department of Homeland Security told the Post it is to run through Oct. 14, and could be extended for another year “should the evaluation of the threat remain the same.”

What is the purpose of the ban?

While media outlets have noted the ban affects countries with predominantly Muslim populations, the nations affected are U.S. allies and are not the same ones covered by President’s controversial travel ban earlier this year. Some reports say the ban comes in response to concerns about a Syrian group’s plot to target airplanes. But, in the absence of a formal statement, it’s hard to say for sure.

Will the device ban improve security?

That’s unclear, too. Some in the security community have expressed puzzlement about the ban. Nicholas Weaver, a researcher at the International Computer Science Institute told the Guardian: “It’s weird, because it doesn’t match a conventional threat model. If you assume the attacker is interested in turning a laptop into a bomb, it would work just as well in the cargo hold. If you’re worried about hacking, a cellphone is a computer.”