It’s scary how much our modern world relies on telecommunications systems, and even scarier that these services are often controlled by a single company in many parts of North America. With a structure like this, a single regional outage could drastically affect normal business activities and day-to-day life. Canada learned this firsthand last week, when a telecom outage wreaked havoc on the nation’s airlines.

On Friday, the Rogers Communications network had a massive outage that affected millions across the country. the company controls 50 percent of Canada’s customer revenue share in the national broadband market. It was a dilemma immediately noticeable for anyone who stepped through Canada’s proverbial front door, the country’s major international airports.

Canada’s airports already ranked near the top of most global lists in terms of delays. The country’s largest airport, Toronto Pearson International, has become in terms of on-time travel. The Rogers outage worsened things dramatically. On Sunday, out of Pearson were delayed. Over 40 percent of flights were delayed out of Montreal and Vancouver airports. And delays are just the tip of the iceberg.

All travelers entering Canada must submit travel and public health information within 72 hours before arrival via ArriveCAN, a government smartphone app. Travelers without smartphones are expected to submit information to ArriveCAN on a computer beforehand and print out a receipt. However, due to its reliance on the Rogers network, the Canada Border Services Agency was unable to process ArriveCAN submissions during the outage. Those waiting to pass through customs were suddenly asked to provide proof of vaccination and a Traveller Contact Information Form in the form of old-fashioned paper documents — a requirement nobody was informed of before they traveled.

The troubles didn’t end after customs. Airport customers were unable to withdraw money from ATMs, and they couldn’t even use credit cards at airport businesses: Interac, Canada’s largest interbank transaction system, was down, because it too relies on the Rogers network.

Obviously, the Rogers network outage extended far beyond the confines of Canada’s airports. According to , city residents had difficulty contacting emergency services via 9-1-1. The second day of had to be conducted via landline phones. All of this is taking place as Rogers is for a $20 billion merger with Shaw Communications. Rogers and competitor Telus currently control 90 percent of the Canadian telecommunications market. That certainly doesn’t seem like it would help the situation.

A previous version of this article misstated that, post-merger, Rogers would control 90 percent of the Canadian telecommunications market. We have updated the text.