TORONTO — Delta Air Lines is telling passengers travelling to the U.S. to arrive at the airport at least three hours before their flight and allow extra time to get through security. The warning comes as new security screenings for all passengers on U.S.-bound flights begin today, with airlines worldwide questioning flyers about their trip and their luggage in the latest Trump administration decision affecting global travel.

Confusion still remains about the new regulations, which come at the end of a 120-day period following the U.S. lifting a ban on laptops in airplane cabins affecting 10 Midde Eastern cities. The new regulations cover all the 2,100 flights from around the world entering the U.S. on any given day.

Some airlines said they had received permission to delay implementing the new rules until January.

Other carriers who announced the new regulations on Oct. 25 included Air France, Cathay Pacific, the Lufthansa Group airlines and EgyptAir.

Both Air Canada and WestJet warned of delays back in the summer. The warnings came soon after the U.S. Homeland Security Department demanded that airlines around the world step up security measures for international flights bound for the U.S. or face the possibility of a total electronics ban for planes, or worse, a ban against flying into the U.S. altogether. The new security rules will apply to roughly 180 foreign and U.S.-based airlines, flying from 280 cities in 105 countries.

At Dubai International Airport, the world’s busiest for international travel, long-haul carrier Emirates began questioning passengers about their luggage, liquids they were carrying and where they were coming from. Passengers also had to have their carry-on bags searched, along with their electronics.

On Wednesday Emirates said it would conduct “passenger pre-screening interviews” for those travelling on U.S.-bound flights in concert with other checks on electronics.

Elsewhere, things did not appear to be going so smoothly. In China, an official in the Xiamen Airlines press office, who would only give his surname as Qiu, said that the airlines received a “demand” about the new U.S. regulations and planned “to take some security measures, including security safety interviews from today on.”

“We’re not going to interview all passengers, but focus on those with a certain degree of risk when checking the passengers’ documents on the ground,” he said.

An official with the Eastern Airlines publicity department said that she saw media reports about security safety interviews but didn’t have immediate details on what her company was doing. An official at the Beijing Airport press centre would only say: “We always strictly follow relevant regulations of the Civil Aviation Administration when conducting security checks.” Both officials spoke on condition of anonymity under regulations.

At Air China, the country’s flag carrier, said it would comply. “We will meet the demands from the U.S. side, but as for the detailed measures (we will take), it is inconvenient for us to release,” he said.

South Korea’s Transport Ministry said that the U.S. agreed to delay implementing the new screening for the country’s two biggest carriers, Korean Air Lines Co. and Asiana Airlines Inc., until next year on condition they deploy staff at boarding gates to monitor travellers.

Royal Jordanian, based in Amman, also has said it would introduce the new procedures in mid-January.

Other airlines with U.S.-bound flights at Seoul’s Incheon International Airport brought in as many as seven extra staff Thursday to question passengers under the new rules but there were no major delays, airport spokesman Lee Jung-hoon said.

Singapore Airlines passengers may be required to “undergo enhanced security measures” including inspection of personal electronic devices “as well as security questioning during check-in and boarding,” the carrier said on its website.

In Hong Kong, passengers described some of the questions they were asked. “They asked me if I packed my own bag, where I packed it from, where I came from, they looked at my itinerary, verify where I was, who I was, from where I came from,” said Fran Young, who was travelling to Los Angeles.

Some showed displeasure. “It’s a little inconvenient, I kind of just want to get my printed ticket and then just go inside,” passenger Gavin Lai said. “I don’t want to wait on people to interview me like that. So it’s a little annoying.”

In March, U.S. officials introduced the laptop ban in the cabins of some Mideast airlines over concerns Islamic State fighters and other extremists could hide bombs inside of them. The ban was lifted after those airlines began using devices like CT scanners to examine electronics before passengers boarded planes heading to the U.S. Some also increasingly swab passengers’ hands to check for explosive residue.

The laptop ban as well as travel bans affecting predominantly Muslim countries have hurt Mideast airlines. Emirates, the region’s biggest, said it slashed 20% of its flights to the U.S. in the wake of the restrictions.

With files from The Associated Press