Most visitors fly into Bozeman Yellowstone International Airport (BZN), about 75 minutes' drive northeast on Highway 84. Rental cars are easy from the airport and a car is essentially required for visiting Ennis — there is no public transport into town. The drive over Norris hill is reliably open year-round.
Coming from the south, the West Yellowstone airport (open only in summer) is about 90 minutes away by Highway 287 along the Madison River.