Another system-wide IT glitch has delayed United Airlines flights worldwide with long lines at many airports late Thursday.
Some flights were delayed for several hours as arriving passengers were held on the tarmac awaiting available gates to deplane.
"Earlier tonight we experienced an issue with our weight reporting system, which caused system wide flight delays. We apologize for the inconvenience," United said it a statement.
The airline said it resolved the issue at about 3.00 am ET and delayed flights were resuming.
United declined say how many flights were delayed or how long the knock-on effect of later departures would continue.
United has so far given no reason for what caused the outage, which saw some flights delayed by up to six hours.
Many angry passengers vented on Twitter.
"Hey
@united, I’ve been stuck on the tarmac for 2 hours on flight UA 732," said user @rubinervin.
"So one little glitch at
@united grounds the entire fleet? Seriously you guys are living in the 1990s," tweeted Randy Bias.
It is the third time United has suffered an IT meltdown in just a few months.
Rival Delta was also hit with a system-wide outage in August, forcing it to cancel more than 2,000 flights.