Is three and a half hours enough for a good nap? Barely. You fall asleep, have a weird dream about moose, and then the pilot announces the descent. You wake up drooling. It’s fine.
Bring a neck pillow if you’re serious about sleep. Or just watch a movie. You can finish The Princess Bride and still have time to watch the landing.
What About the Return Flight?
Going back from Seattle to Anchorage is a different beast. It takes longer—about 3 hours 45 minutes to 4 hours 15 minutes. Why? Because you’re fighting the jet stream. The wind is now in your face.
Also, you gain an hour on the way back. Leave Seattle at 7:00 PM, land in Anchorage at 9:45 PM. You feel like you cheated time. But you didn’t. It’s just Alaska being weird.