The sudden closure of the country's 71st busiest airport by the Federal Aviation Administration stranded air travellers and disrupted medical evacuation flights overnight, in what appeared to be an unprecedented action by the US government.
The FAA initially said the closure would last 10 days before lifting it after about seven and a half hours.
Government and airline officials, speaking on condition of anonymity, told Reuters the FAA closed the airspace due to concerns that a laser-based counter-drone system being tested by the US military could pose risks to air traffic.
The Pentagon planned to test a laser for use in shooting down drones used by Mexican drug cartels, three people familiar with the situation told the Associated Press.
The FAA lifted its restrictions after the army agreed to more safety tests before using the system, which is being tested at Fort Bliss, next to El Paso International Airport.
The White House was surprised by the El Paso airspace closure, according to two sources speaking on condition of anonymity, touching off a scramble among law enforcement agencies to figure out what happened.
The FAA lifted the restrictions shortly after the situation was discussed in the office of White House chief of staff Susie Wiles, the sources said.
US Transportation Secretary Sean Duffy, who oversees the FAA, said the closure had been prompted by a drone incursion by a Mexican drug cartel.
However, a drone sighting near an airport would typically lead to a brief pause on traffic, not an extended closure, and officials say drone incursions in the El Paso region are common.
The move had stranded numerous aircraft from Southwest Airlines, United Airlines and American Airlines at the airport, which handles about four million passengers annually.
El Paso mayor Renard Johnson said the FAA did not reach out to the airport, the police chief or other local officials before shutting down the airspace.
"I want to be very, very clear that this should have never happened," he said at a news conference.
The US official in charge of airport security, Transportation Security Administration Acting Administrator Ha Nguyen McNeill, also told Congress that she had not been notified.
"That's a problem," said Republican representative Tony Gonzales of Texas, who said there are daily drone incursions along the US-Mexico border.
Trump has repeatedly threatened to deploy US military force against Mexican drug cartels, which have used drones to carry out surveillance and attacks on civilian and government infrastructure, according to US and Mexican security sources.
Mexican President Claudia Sheinbaum said at her daily news conference that her administration would try to find out what exactly happened but had no information about drone traffic along the border.
with AP
