If you’re flying to America, you’ll need to get to the airport another hour earlier

Nobody is quite sure what they are, yet, but new airport security measures take effect today which will lengthen security screening times for passengers headed to the United States.

The Department of Homeland Security announced last month that it would be upping security measures for airports in 105 countries with direct flights to the U.S., including passenger screening, checks on personal electronics, and checks of airports and airplanes themselves.

What exactly that means, however, remains to be seen.

It seems that the new delays will be aimed at larger electronic devices.

A press release from Canadian airline Westjet warned anyone travelling with a device larger than a cellphone that there would be more screening measures for laptops and tablets.

Transport Canada, which manages airport security, reached out to VICE News after this story was published to insist that the measures would enhance security, but refused to discuss details. “Details regarding specific security measures and where they apply cannot be disclosed for security reasons,” the statement reads.

Dionisio D’Aguilar, tourism and aviation minister for the Bahamas, told a local newspaper that delays due to screening may only get worse.

“We are now at two hours, that may go up to three or even a little more. We are not 100 percent sure at this time and we know that it is going to be a little rocky in the beginning,” D’Aguilar said.

Homeland Security Secretary John Kelly has pegged the new measures to credible threats to American airlines by terrorist groups. Similar intelligence appears to be behind his decision to ban laptops and larger electronic devices from carry-on luggage for flights originating from a handful of Middle East countries — a ban that is now effectively over, as those countries have implemented new electronic screening procedures.

In justifying the new measures, Kelly told a security conference in late June that terror groups see American aviation as a “crown jewel.”

Homeland Security says the new measures will stay in place “until the threat changes.”