Allegiant Air's senior vice-president of operations Kris Bauer will retire, effective 1 September.
Bauer, however, will continue to work for Allegiant in a part-time role on special projects, says the airline.
"Despite our best efforts to convince him otherwise, Kris has decided that this is the right time for him to step down and enjoy an early retirement," says Andrew Levy, Allegiant's president. "We are grateful for his many contributions and look forward to his continued contributions in his new role."
Bauer had worked for three years at Allegiant, during which the airline added Boeing 757s and Airbus A320 family aircraft to its fleet.
Allegiant says it will search for a successor to replace Bauer.