Tempers boiled in departure lounges around the world overnight as two separate problems with United Airlines' computer systems caused widespread delays.
The airline initially told NBC News early Friday that 63 flights were affected, but spokeswoman Maddie King later retracted that figure and said it was just "a small number of flights."
The first glitch, concerning United's luggage weighing systems, was resolved late Thursday, King said. Another issue caused more delays before being resolved at 3 a.m. ET — although King said she did not know its nature nor its cause.
Passengers vented their frustrations on social media, posting pictures and messages from San Francisco and Newark to Costa Rica and London.
Amy Zandy, a 32-year-old sales director from Chicago, was among those affected.
"You are literally a global conglomerate," she told NBC News, referring to United. "You don't have backup systems? You don't know how to manually process this information?"
Zandy was with her boyfriend waiting to board a United flight from San Francisco to San Diego. They were making a layover on a trip back from a vacation in Hawaii, which she said was already cut short by yet another problem with United's computer systems.
"People are p***ed," Zandy said about those standing in the line. "They're losing their minds."
She said one elderly couple had covered themselves with blankets and were resting on pillows.
"We feel trapped," Zandy added.
Roxanne Lott, 46, was waiting for a flight from Newark to Dublin, Ireland.
"We sat on the tarmac for almost three hours," said Lott, who works in online marketing.
The glitch appeared to be smaller than another involving United Airlines' computer systems in July that affected some 3,500 flights.