Passengers arriving at Toronto Pearson International Airport on Thursday morning where met with significant delays after a group of travellers were mistakenly allowed to flow through the wrong door. 

At approximately 8:30 a.m., the airport provided an update on the error, revealing that a crowd of passengers at the Terminal 1 transborder were being held after arriving travellers passed through the wrong door, causing a security breach. 

Passengers at T1 transborder are holding this morning after arriving passengers were allowed to flow through the wrong door. We will update as information becomes available. pic.twitter.com/a1DH9mns4w

— Toronto Pearson (@TorontoPearson) November 9, 2023

As a result of the breach, multiple connecting flights to the U.S. were delayed as airport officials tried to work out the issue. 

"This morning's disruption was caused by a ground handler contacted to an airline, who directed domestic passengers to an area of screened transborder passengers," the airport confirmed on X. 

We are being told by gate agents that the airport is "on lockdown" and has been for over an hour.

— Steve Taggart (@wyosyeveo) November 9, 2023

Affected customers quickly took to social media to air out their frustrations and called out airport officials for the "lack of communication" and infrequent status updates. 

Current lineup at NEXUS.
Not right.
Let’s get this moving so we can make our flights pic.twitter.com/PBCd2FtZwV

— joseph young (@jryoungglobal) November 9, 2023

"Definitely going to run out of beer and coffee in a few hours...@TorontoPearson. Please consider updating passengers in a timely manner just so everyone can relax a bit," one customer wrote. 

Airport operations at Terminal 1 domestic, international, and Terminal 3 gates remain unaffected by the error. 

Toronto Pearson and USCBP are working with airlines to identify flights that can board.

— Toronto Pearson (@TorontoPearson) November 9, 2023

"USCBP has now restarted pre-clearance processing, and transborder flights are resuming," the airport tweeted shortly before 10:30 a.m.