United Airlines is still scrambling to get back on track after technology problems tied the airline in knots early Wednesday.
United expects to have flights back to normal by Thursday morning, one day after there was an unusual scene at airports across the country.
At Chicago's O'Hare International Airport this morning, all of United's flights were lined up in a row, with no place to go as a computer glitch halted all flights.
It was the same story in other major cities, including San Francisco, Los Angeles and Denver as all of United's 268 scheduled departures between 8 and 10 a.m. Central time were grounded due to a computer problem.
Flights already in the air were allowed to continue.
"It was unexpected and very ... inconvenient for everyone," one passenger commented.
Another stranded traveler said, "I don't want to blame anyone. I just want to get out of here."
The computer which failed in Chicago was in charge of dispatching flights from one airport to another, among other crucial details.
"That's what tells how much fuel should be onboard, where the pilot should fly, how they should fly and how much cargo can be onboard," said aviation consultant Michael Boyd. "Without that, you are shut down. You are dead."
Why it failed was anyone's guess.
"I don't know the cause," said United Airlines spokesperson Megan McCarthy. "We don't know in terms of what exactly happened."
For several hours after the computers were back up and running, lines at customer service desks in airports lengthened, and the airline still had no answer.
"They should have an official out in the first 10 minutes. That's a huge failure," Boyd said. "The airline should be out there with someone explaining it as quickly as possible."
With late departures up 10 percent this year already, and with flights on all airlines now expected to be better than 80 percent full, any delay can throw the whole system off.
"The system is wrapped so tightly right now that any disruption like this becomes a major problem for 24, up to 72 hours," said airline consultant Terry Trippler.
While United said it hopes to be back to normal by Thursday morning, the company still urges passengers to check the status of their flights before heading for the airport. That's good travel advice on any day.