Fly SFO → Kalispell/Glacier Park International (FCA). United nonstop, ~2h 40m. Pick up rental car at FCA — all major agencies at the terminal. Drive 15 minutes north to Whitefish.
Start early (before 7am) to beat Logan Pass parking. The full Going-to-the-Sun Road is open in August and is one of the most scenic drives in America. Enter at West Glacier (25 min from Whitefish).
Drive GTTSR to the east side (or take the free park shuttle). The St. Mary side of the park has a drier, more dramatic feel with big open valleys and striking peaks.
Morning rafting on the Middle Fork of the Flathead River, then a relaxed afternoon at Flathead Lake or Whitefish Lake.
Morning options depending on your flight time:
If you extend to Wednesday August 12 (10 days total), here's how to fill the extra days. This version adds a night at Flathead Lake and two at Many Glacier — the crown jewel of the park that most visitors skip.
Instead of flying home, stay in Missoula and take a day trip south to Flathead Lake, or relocate up to Polson/Bigfork on the lake.
Drive from Flathead Lake/Bigfork to Many Glacier (~3h via US-89 through the Blackfeet reservation). This is the most spectacular valley in Glacier — towering peaks, turquoise lakes, and the best wildlife viewing. Stay at Many Glacier Hotel (historic lodge on Swiftcurrent Lake) or Swiftcurrent Motor Inn.
Drive Many Glacier → Kalispell (~2.5h via Babb and US-2). Return rental car at FCA. Fly FCA → SFO (United nonstop, ~2h 40m). This version avoids the MSO return flight scheduling issue entirely since FCA has more SFO flight options.