Thousands of United Airlines passengers worldwide were stranded on Wednesday morning, after a computer glitch forced the American airline major to ground around 3,500 flights across the globe for several hours.
"We experienced a network connectivity issue this morning," United Airlines confirmed in a statement after 9 am ET, NBC News reported.
"We are working to resolve this and apologise to our customers for any inconvenience."
The Federal Aviation Administration (FAA) blamed it on "automation issues."
United Airlines' regional carriers began plying on their normal routes at around 9:20 am. While according to Buffalo News, the airline resumed its services at the Buffalo Niagara International Airport at 9.40 am local time, lifting the ban imposed at 8 am.
On 2 June also, United flights were grounded due to "automation issues."
On Twitter, United Airlines was a top trend in United States with hundreds of passengers posting images of long queues at the airlines gateway.
"We don't know everything behind this morning's issues yet, but today's incident underscores the sense that something is very wrong at United," WTop quoted Gary Leff, co-founder of frequent-flier website MilePoint as saying.
During the ground stop, 235 domestic and 138 international destination flights were affected.
Carlos Aquino @dircasacalora
United Airlines Flights Grounded Across the US for 2nd Time
Ken Tate @KenTate83
I'm not saying the United Airlines issue is due to a cyberattack, but this just shows the potential impact...on a 'tip of the iceberg' scal...
Fran Spielman @fspielman
Not your typical summer travel nightmare. Computer problems cause temporary United Airlines total ground stop:
BREAKING: FAA informs that ground stop affecting United Airlines flight has been lifted.
T. E. Nolan @d_marmalade
United Airlines works hard every day to make train travel more popular.
— Ashley Yore (@AshleyYore) July 8, 2015