Frontier Terminal Las Vegas is the older terminal and is divided into four concourses: A, B, C, and D. Concourse D is dedicated to international flights, while the other concourses primarily serve domestic flights.Frontier Terminal Las Vegas also known as the "E Gates," is a newer facility that primarily serves international airlines and some domestic carriers.
https://www.airlineshubs.com/airport/frontier-airlines-harry-reid-international-airport-terminal-las/