Major international airlines canceled flights or changed aircraft routes heading to the United States yesterday. It’s the latest complication in worries over 5G mobile phone service. Could the new technology interfere with airplane frequencies?

Mobile carriers AT&T and Verizon agreed this week to pause the rollout of the new 5G high-speed wireless service near key airports. But some airlines say they received warnings that the Boeing 777 was particularly affected by the new service.

Carriers took widely different approaches to the brewing crisis affecting international travel.

Yesterday, Emirates—the largest airlines based in the United Arab Emirates—announced it would halt flights to several American cities due to “operational concerns associated with the planned deployment of 5G mobile network services in the U.S. at certain airports.”

Tim Clark, president of Emirates, called the 5G fiasco “one of the most delinquent, utterly irresponsible” situations he’d ever seen as it involved a failure by government, science, and industry.

Air India, British Airways, Japan Airlines, and Japan’s All Nippon Airways all canceled flights to cities such as Chicago, Newark, Los Angeles, and New York.

Korean Air, Hong Kong’s Cathay Pacific, and Austrian Airlines substituted different planes for flights that were scheduled to use 777s.

Meanwhile, Air France plans to continue flying Boeing 777s into American airports. It did not explain why it didn’t change its aircraft as many other carriers have.

Dozens of countries have deployed similar high-speed mobile networks. However, there are some key differences in how the U.S. network operates.

The new 5G networks use a segment of the radio spectrum that is close to that used by radio altimeters. Altimeters measure the height of aircraft above the ground and help pilots land in low visibility.

The U.S. Federal Communications Commission (FCC) sets a buffer between the 5G frequency and the one altimeters use. Officials there determined that it could be used safely near air traffic.

But Federal Aviation Administration (FAA) officials see a potential problem. So telecom companies AT&T and Verizon agreed to a pause on Tuesday. The two companies spent tens of billions of dollars for the 5G spectrum known as C-Band in a government auction last year.

Among the problems that may make the 5G rollout an issue in the United States and not other countries, are: 1) that American towers use a more powerful signal strength than those elsewhere; 2) the network operates on a frequency closer to the one altimeters use; and 3) tower antennae point up at a higher angle.

FCC chairwoman Jessica Rosenworcel urged the FAA to conduct its safety checks with “both care and speed.”

(An Emirates jetliner comes in for landing at the Dubai International Airport in Dubai, United Arab Emirates. AP/Jon Gambrell)