You have three options when flying:
1) Fly into Phoenix, then rent a car and drive @ 225 miles (4 hours).
Usually the most cost effective option.
Driving directions from Phoenix, AZ Airport
Phoenix Sky Harbor International Airport
Map of Phoenix Sky Harbor Airport Terminals
2) Fly into Flagstaff, then rent a car and drive @ 85 miles (1½ hours). Requires flying into Phoenix first, then taking a separate flight to Flagstaff. Smaller aircraft is used to fly between Phoenix and Flagstaff.
Driving directions from Flagstaff, AZ Airport
3) Fly into Las Vegas, then rent a car and drive @ 275 miles (4½ hours).
Driving directions from Las Vegas, NV Airport
Las Vegas McCarran International Airport
Map of Las Vegas McCarran Airport Terminals
Other transportation alternatives (trains, buses, etc) may be found on the official Grand Canyon National Park website.