More than 1.5 million customers have travelled on the United Airlines service to and from Newark Liberty International Airport in New Jersey since its launch in 1998, operators say.
A celebration marking the 15th anniversary of the service was held at Glasgow Airport today.
Campbell MacKinnon, operations director at the airport, said: “Not only does it generate considerable in-bound tourism revenue for Glasgow and Scotland, it allows businesses to access and trade with what is the world’s largest economy.
“Routes such as this enable Scotland to maintain and increase its global competitiveness.”
VisitScotland chairman Mike Cantlay said: “Efficient airline connectivity is key to Scottish tourism in a 21st century landscape.
“This long-standing United Airlines route has done just that for 15 years, bringing visitors to our shores and generating millions for the Scottish economy.”