The measures are being introduced on all US-bound flights to comply with government requirements aimed at responding to threats of hidden explosives, according to the airlines.
The new measures could include short security interviews with passengers at check-in or at the boarding gate, prompting worries about concerns over flight delays and a longer airport processing time.
According to estimates, the new measures will affect well over 300,000 airline passengers on about 2,100 commercial flights arriving daily in the United States, on 180 airlines from 280 airports in 105 countries.
US Transportation Security Administration officials are giving some airlines or airports additional time to comply with the new interviews as long the US government has approved security plans by today, Thursday.
The United States announced the new rules in June to end its restrictions on carry-on electronic devices on planes coming from 10 airports in eight countries in the Middle East and North Africa in response to concerns that explosives could be hidden in electronic devices.
Those restrictions were lifted in July, but the Trump administration said it could reimpose measures on a case by case basis if airlines and airports did not boost security.
European and US officials said at the time that airlines had 120 days to comply with the measures, including increased passenger screening.
Airlines have expressed concerns with the new measures.
