Travelers flying United late Thursday reported hours of delays after the airline was hit by a widespread computer problem.
United ( said it experienced an issue with its weight reporting system that was later resolved. )
"Any delayed flights are resuming and we apologize again for the inconvenience," the company tweeted a little after 3 a.m. ET.
A spokesperson was unable to provide any information on how bad the delays were and what the knock-on effects might be for United's network.
Unhappy passengers across the U.S. took to social media to vent their frustration.
"Hey @united, I've been stuck on the tarmac for 2 hours on flight UA 732," said Twitter user @rubinervin.
"So one little glitch at @united grounds the entire fleet? Seriously you guys are living in the 1990s," tweeted Randy Bias.
United's woes are the latest in a string of recent system problems at major airlines. Last month, British Airways suffered a computer problem that caused delays and long lines at airports in the United States and Europe.
-- Jethro Mullen and Daniel Allman contributed to this report.