The justices on Monday left in place a lower court ruling that said Boston-based Flytenow could not operate a website that connected private pilots with passengers willing to share fuel costs and other flight expenses.
The Federal Aviation Administration shut down the website in 2015 after finding that the service violated flight regulations.
Cost-sharing arrangements have long been allowed through word of mouth, bulletin boards and email. But the FAA said using a website was like advertising and subjected those pilots to the same elaborate safety regulations as commercial airlines.
Flytenow argued that it was applying modern technology to a practice that has been around for decades.
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