A computer system glitch left thousands of United Airlines passengers across the globe grounded Wednesday, causing a ripple effect of heavy delays throughout major airports.
About 3,500 flights were affected and the airline sought to recover after the ground stop was lifted. Aviation experts said that delays of even 90 minutes could have a snowball effect triggering flight delays at each late flight's destination.
The delays could reach 235 domestic and 138 international destinations.
"We experienced a network connectivity issue this morning," United confirmed in a statement after 9 a.m. "We are working to resolve this and apologize to our customers for any inconvenience."
The Federal Aviation Administration specifically blamed the ground stop on "automation issues."
The ground stop, however, was lifted around 9:20 a.m. for United's regional carriers, which can perform their own weight and balance checks.
Passengers at airports from Albuquerque, New Mexico, to Washington, D.C., to Florida complained of system backups and long lines. Gate agents at some locations were forced to write tickets by hand.
NBC Connecticut said United passengers without a hard copy of their boarding pass were not being allowed to check in at Bradley International Airport in Windsor Locks, north of Hartford.
Tom Costello contributed reporting. This article originally appeared on NBCNews.com. This is a developing story. Please fresh this page for updates.