The US government has confirmed it is considering anti-terrorist passenger checks on aircraft overflying the United States.
The proposal would mean foreign airlines would be required to check the names of passengers on all flights over the US against government watch lists.
The plan would mostly affect airlines in Mexico and Canada because most of the hundreds of overflights each day come from those countries.
Currently, foreign airlines planning to land in the United States must submit passenger and crew lists to the government within 15 minutes of departure from abroad. The names are checked against lists of people considered terrorists or who otherwise could present a danger.
Airlines must do the same for crew members on flights over the United States.
The proposed requirement to check names of passengers as well comes after an incident on April 8th, when US authorities denied a KLM Amsterdam-to-Mexico flight the right to fly into US airspace.
The action came after US officials learned that two Saudi passengers aboard the plane were on the government's "no-fly" list of known or suspected terrorists.
The plane had been in the air five hours and was in Canadian airspace when it was refused entrance into US airspace, according to a KLM Royal Dutch Airlines spokesman.
The plane returned to Amsterdam because it was assigned to a Canadian airport that could not handle a reconfigured Boeing 747 carrying 278 people and 15 horses. The passengers went on to London and returned to Saudi Arabia.